This study was supported by a grant from the European Union&#39;s Horizon 2020 Work Programme (call H2020-FETOPEN-2018-2020) under grant agreement 964712 (PRIME; to M. Simonato).

Cerebrospinal Fluid and Blood Withdrawal from Rats with Concurrent EEG Recording

<ol>
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The authors have nothing to disclose.

The present work illustrates an easy-to-master technique of CSF and blood collection in rats, which may be useful not only for studies in models of epilepsy but also of other neurological conditions or diseases such as Alzheimer, Parkinson, or multiple sclerosis. In epilepsy research, both sampling procedures coupled with video-EEG are ideal when a correlation between the levels of different soluble molecules and seizure activity is pursued. For this specific reason, a continuous video-EEG recording was employed: i) in order to correctly diagnose epilepsy or ii) to monitor the different phases of the disease progression, and/or iii) to correlate sampling with the occurrence of spontaneous seizures. Such sampling techniques can be performed in anesthetized rats, thus causing minimal stress.
Critical steps, troubleshooting, method limitations 
The protocol has some critical technical steps. Firstly, it can be difficult to find the correct place for CSF collection at the first attempt. If the operator misses the cisterna magna at the first attempt, any subsequent trial would be blood contaminated, as the animal will bleed from the needle wound. From this point of view, the success in the collection is heavily dependent on the operator&#39;s skill. Secondly, some steps of blood withdrawal need special attention. In particular, there is a high risk of hemolysis if the operator rubs the tail too vigorously with ethanol, if the temperature of the water used for the tail vein vasodilation is higher than 42 &#176;C, or if the blood in the collection tube is mixed with anticoagulant too energetically. Another peculiarity of blood collection in chronic epileptic animals is the influence of their bradycardia on the rate at which blood drops out of the tail vein33. If this is too slow, the blood may coagulate on the walls of the collection tube. To avoid this problem, one option is to split the sampling into two collection tubes, reducing the volume of blood/tube. Finally, there is one pitfall that is intrinsic to epilepsy studies. The stress provoked by animal manipulation before sampling may induce seizures, which in turn may interfere with the levels of molecules under the investigation34. Whenever it is possible, place the anesthesia induction chamber into the home cage and allow the animal to enter it spontaneously. As a modification of the proposed protocol, a restrainer can be used to perform blood withdrawal without isoflurane anesthesia. However, this can be done in telemetry, but not in tethered animals, because tethered rats may lose their head implants during this procedure.
Having a well-trained operator and posing maximum effort to avoid stress, the only limitation of the present protocol is the maximal volume that can be withdrawn without compromising the animal&#39;s health. According to current standards, it is recommended to collect a maximum of 100 &#181;L of CSF for 4x over 15 days in a single animal32. Similarly, it is suggested to collect less than 10% of total blood body volume on a single sampling and less than 15% of total blood body volume in 28 days30,31.
Comparison of the method with other techniques 
Proposed time-resolved CSF and plasma sampling approaches have several advantages with respect to existing alternative methods. First, a cisterna magna puncture used to sample CSF in epileptic rats has a lower risk of head implant loss in comparison to a cannulated system if coupled to tethered EEG. In contrast to puncture procedures, the cannula attached to the electrode by dental cement (bulky and heavy for animals&#39; heads), while solicited by repeated attachments/detachments to the CSF withdrawals, is much more prone to being lost over multiple days of sampling. Indeed, the success rate results show how some cannulated animals (N/A) do not arrive at the advanced sampling time points, thus their respective samples are lost (Table 1). Additionally, the puncture method seems to be superior to cannulated approach in terms of better sterility and reduced meningeal reaction with limited increase of cell and albumin content in CSF, as has been previously documented by other22,35,36. The degree of CSF leukocytes and albumin contamination may be important for the validity of methods used for epilepsy biomarkers quantification35. Second, the free fall dropping method of blood plasma sampling used for repeated measures is superior to any other withdrawal method as it is not terminal (non-recovery), unlike the decapitation, cardiac puncture, abdominal/thoracic blood vessel or retro-orbital withdrawal and allows multiple blood sampling. It is simpler than many tail vein blood vacuum withdrawal techniques, as it does not require tubing28,37 and produces hemolysis-free plasma samples of high quality for further sncRNA analyses focused on identifying putative biomarkers of epileptogenesis38. The absence of free hemoglobin in the samples, when employing the drop sampling technique or avoiding the tail milking, was confirmed by low absorbance results of the plasma samples (Table 2) in line with previously published procedures suitable for the evaluation of sncRNA plasma content39,40.
Applications and future directions 
The above-described methods may be applied to measure soluble molecules of interest in any model of neurological diseases. A specific example is the sampling of biological liquids for the identification of potential/putative epilepsy biomarkers. There is an urgent unmet medical need to discover these biomarkers for people with epilepsy, especially prognostic and susceptibility/risk biomarkers, as they do not yet exist.
In conclusion, the present protocol is feasible in rats, including epileptic rats, and is easy to actuate for trained individuals. Moreover, it permits multiple high-quality sampling in longitudinal studies in compliance with the principle of 3Rs (i.e., replacement, reduction, and refinement)41.

Cerebrospinal fluid (CSF) and blood sampling are important to identify and validate biomarkers of epilepsy, in both preclinical and clinical research1,2. Nowadays, the diagnosis of epilepsy and most of the research on epilepsy biomarkers focus on EEG and neuroimaging3,4,5. These approaches, however, present several limitations. Apart from routine scalp measurements, in many cases, EEG requires invasive techniques like depth electrodes6. Brain imaging methods have poor temporal and spatial resolution and are relatively expensive and time-consuming7,8. For this reason, the identification of non-invasive, low-cost, and biofluid-based biomarkers would provide a very attractive alternative. In addition, these biofluid biomarkers could be combined with available diagnostic approaches to sharpen their predictiveness.
Patients diagnosed with epilepsy are routinely submitted to EEG9,10 and blood sampling11,12,13,14, and many also to CSF withdrawal to exclude life-threatening causes (i.e., acute infections, autoimmune encephalitis)15. These blood and CSF samples can be used in clinical research aiming to identify biomarkers for epilepsy. For example, Hogg and co-workers have found that an increase in three plasma tRNA fragments precedes seizure occurrence in human epilepsy14. Similarly, interleukin-1beta (IL-1&#946;) levels in human CSF and serum, expressed as ratio of IL-1&#946; levels in CSF over serum, can predict post-traumatic epilepsy development after traumatic brain injury16. These studies highlight the importance of biofluids sampling for epilepsy biomarkers research, but they face multiple limitations intrinsic to clinical trials, e.g., the cofounding factor of anti-epileptic drugs (AEDs) in blood, the frequent lack of etiology information, inadequate controls, modest numbers of patients, and others17,18.
Pre-clinical research offers other opportunities for investigating molecules in biofluids as potential biomarkers for epilepsy. In fact, it is possible to withdraw plasma and/or CSF from animals while performing EEG recordings. Moreover, sampling can be performed repeatedly across multiple days of the experiment, and a number of age, sex, and epileptic insult-matched controls can be used to improve the study&#39;s robustness. Here, a flexible technique to obtain CSF from cisterna magna with parallel withdrawal of plasma from the tail vein in EEG-monitored rats is described in detail. The presented technique has several advantages over alternative methods. By using a butterfly needle approach, it is possible to collect CSF several times without compromising the function of EEG electrodes or similar head implants. This represents a refinement of intrathecal catheter withdrawal procedures, which are associated with a relatively high risk of infection. In addition, the reported free fall dropping approach used for blood collection is superior to other approaches of tail vein blood withdrawal because of the highly reduced risk of hemolysis, due to the fact that blood does not pass through tubing and no vacuum pressure is applied. If performed under strict germ-free conditions, there is a particularly low risk of infection for animals. In addition, by starting the blood withdrawals at the very end of the animals&#39; tails, sampling can be repeated several times. Such techniques are easy to master and can be applied in many preclinical studies of central nervous system disorders.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Blood collection set BD Vacutainer Safety-Lok</td>
			<td>BD Italy SpA, Milan, Italy</td>
			<td>367246</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Blood Collection tubes (Microtainer K2E)</td>
			<td>BD Italy SpA, Milan, Italy</td>
			<td>365975</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Butterfly Winged Infusion Set 23G x 3/4&#39;&#39; 0.6 x 19 mm</td>
			<td>Nipro, Osaka, Japan&#160;</td>
			<td>PSY-23-ET-ICU</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Centrifuge refrigerated ALC PK 130R</td>
			<td>DJB Labcare Ltd, Buckinghamshire, England</td>
			<td>112000033</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Cotton suture 3-0</td>
			<td>Ethicon, Johnson &#38; Johnson surgical technologies, Raritan, New Jersey, USA</td>
			<td>7343H</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Diazepam 5 mg/2ml, Solupam</td>
			<td>Dechra Veterinary Products, Torino, Italy</td>
			<td>105183014 (AIC)</td>
			<td>Solution</td>
		</tr>
		<tr>
			<td>Digital video 8-channel media recorder system of telemetry EEG set up</td>
			<td>Data Sciences International (DSI), St Paul, MN, USA</td>
			<td>PNM-VIDEO-008</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Digital video surveillance system of tethered EEG set up</td>
			<td>EZVIZ Network, Hangzhou, Cina</td>
			<td>EZVIZ (V5.3.2)</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Disinfectant based on stabilized peroxides and quaternary ammonium activity</td>
			<td>Laboratoire Garcin-Bactinyl, France</td>
			<td>LB 920111</td>
			<td>Solution</td>
		</tr>
		<tr>
			<td>Dummy guide cannula 8 mm</td>
			<td>Agn Tho&#39;s, Lindig&#246;, Sweden</td>
			<td>CXD-8</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Electrode 3-channel two-twisted</td>
			<td>Invivo1, Plastic One, Roanoke, Virginia, USA</td>
			<td>MS333/3-B/SPC</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Electrode holder for stereotxic surgery</td>
			<td>Agn Tho&#39;s, Lindig&#246;, Sweden</td>
			<td>1776-P1</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Eppendorf BioSpectrometer basic</td>
			<td>Eppendorf AG, Hamburg, Germany</td>
			<td>6137</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td> 
			Eppendorf PCR Tubes 0.2 mL</td>
			<td>Eppendorf Srl, Milan, Italy</td>
			<td>30124332</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Eppendorf &#956;Cuvette G1.0</td>
			<td>Eppendorf AG, Hamburg, Germany</td>
			<td>6138</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Feeding needle flexible 17G for rat</td>
			<td>Agn Tho&#39;s, Lindig&#246; Sweden</td>
			<td>7206</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Grass Technology apparatus</td>
			<td>Grass Technologies, Natus Neurology Incorporated, Pleasanton, California, USA</td>
			<td>M665G08</td>
			<td>Equipment (AS40 amplifier, head box, interconnecting cables, telefactor model RPSA S40)</td>
		</tr>
		<tr>
			<td>Isoflurane 100%, IsoFlo</td>
			<td>Zoetis, Rome, Italy</td>
			<td>103287025 (AIC)</td>
			<td>Solution</td>
		</tr>
		<tr>
			<td>Ketamine (Imalgene)</td>
			<td>Merial, Toulouse, France</td>
			<td>221300288 (AIC)</td>
			<td>Solution</td>
		</tr>
		<tr>
			<td>Lithium chloride&#160;</td>
			<td>Sigma-Aldrich, Milan, Italy</td>
			<td>L9650</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Microinjection cannula 31G 9 mm</td>
			<td>Agn Tho&#39;s, Lindig&#246; Sweden</td>
			<td>CXMI-9</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>MP150 modular data acquisition and&#160;analysis system&#160;</td>
			<td>Biopac, Goleta, California, USA</td>
			<td>MP150WSW</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Ophthalmic vet ointment, Hylo night</td>
			<td>Ursapharm, Milan, Italy</td>
			<td>941791927 (AIC)</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Pilocarpine hydrochloride</td>
			<td>Sigma-Aldrich, Milan, Italy</td>
			<td>P6503</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>PTFE Tube with joint</td>
			<td>Agn Tho&#39;s, Lindig&#246;, Sweden</td>
			<td>JT-10</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Saline</td>
			<td>0.9% NaCl, pH adjusted to 7.0</td>
			<td></td>
			<td>Solution</td>
		</tr>
		<tr>
			<td>Scopolamine hydrobromide trihydrate</td>
			<td>Sigma-Aldrich, Milan, Italy</td>
			<td>S2250</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Scopolamine methyl nitrate</td>
			<td>Sigma-Aldrich, Milan, Italy</td>
			<td>S1876</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Silver&#160;sulfadiazine 1% cream&#160;</td>
			<td>Sofar, Trezzano Rosa, Milan, Italy</td>
			<td>025561010 (AIC)</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Simplex rapid dental methacrylic cement&#160;&#160;</td>
			<td>Kemdent, Associated Dental Products Ltd, Swindon, United Kingdom</td>
			<td>ACR811</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Stereotaxic apparatus</td>
			<td>David Kopf Instruments, Los Angeles, CA, USA</td>
			<td>Model 963</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Sucrose solution</td>
			<td>10% sucrose in distilled water</td>
			<td>Home-made</td>
			<td>Solution</td>
		</tr>
		<tr>
			<td>Syringe 1 mL&#160;</td>
			<td>Biosigma, Cona, Venezia, Italy</td>
			<td>20,71,26,03,00,350</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Telemeters</td>
			<td>Data Sciences International (DSI), St Paul, MN, USA</td>
			<td>CTA-F40</td>
			<td>Material</td>
		</tr>
		<tr>
			<td>Telemetry EEG traces analyzer</td>
			<td>Data Sciences International (DSI), St Paul, MN, USA</td>
			<td>NeuroScore v3-0</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Telemetry system</td>
			<td>Data Sciences International (DSI), St Paul, MN, USA</td>
			<td>Hardware plus software Ponemah core 6.51</td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Xylazine hydrochloride</td>
			<td>Sigma-Aldrich, Milan, Italy</td>
			<td>X1251</td>
			<td>Material</td>
		</tr>
	</tbody>
</table>

sampling cerebrospinal fluid and blood from lateral tail vein in rats during eeg recordings

Because the composition of body fluids reflects many physiological and pathological dynamics, biological liquid samples are commonly obtained in many experimental contexts to measure molecules of interest, such as hormones, growth factors, proteins, or small non-coding RNAs. A specific example is the sampling of biological liquids in the research of biomarkers for epilepsy. In these studies, it is desirable to compare the levels of molecules in cerebrospinal fluid (CSF) and in plasma, by withdrawing CSF and plasma in parallel and considering the time distance of the sampling from and to seizures. The combined CSF and plasma sampling, coupled with video-EEG monitoring in epileptic animals, is a promising approach for the validation of putative diagnostic and prognostic biomarkers. Here, a procedure of combined CSF withdrawal from cisterna magna and blood sampling from the lateral tail vein in epileptic rats that are continuously video-EEG monitored is described. This procedure offers significant advantages over other commonly used techniques. It permits rapid sampling with minimal pain or invasiveness, and reduced time of anesthesia. Additionally, it can be used to obtain CSF and plasma samples in both tethered and telemetry EEG recorded rats, and it may be used repeatedly across multiple days of experiment. By minimizing the stress due to sampling by shortening isoflurane anesthesia, measures are expected to reflect more accurately the true levels of investigated molecules in biofluids. Depending on the availability of an appropriate analytical assay, this technique may be used to measure the levels of multiple, different molecules while performing EEG recording at the same time.

The outcome of different CSF and blood withdrawal procedures performed in 9 control and 18 chronic epileptic rats, all implanted with electrodes at 1-month post-SE, is reported in terms of success rate. After implantation, all rats were video-EEG monitored for 1 month, during which the CSF plus blood was withdrawn 5x every 3 days during the two last weeks of the experiment (i.e., at days 52, 55, 58, 61, and 64 post-SE; dpSE). Data from multiple withdrawals in different animals were used to compare the success rate of CSF collection in the double-head implant-endowed rats (cannulated for CSF withdrawal) with the success rate of CSF collection (carried out by cisterna magna puncture) in only tethered or telemetry electrodes implanted animals (Table 1). In different animals, the impact of vacuum blood collection or tail milking on the quality of plasma samples was evaluated (Table 2). For this purpose, UV spectrophotometry analysis at 414 nm was used for the detection of free hemoglobin. For statistical analyses, commercial software was used, and Kruskal-Wallis or one-way ANOVA with post-hoc Tukey&#39;s multiple comparison tests were used (p&#60;0.05 considered statistically significant). The data are expressed as a mean &#177; SEM.
Success rate of multiple CSF sampling in cannulated and punctured rats 
CSF has been sampled 5x within 2 weeks in 3 groups of rats: (i) cannulated and tethered electrode implanted rats (CT group of animals); in these, the CSF withdrawal was performed via dummy guide cannula and PTFE tubing joint to 1 mL syringe when they were non-anesthetized and freely moving under video-EEG; (ii) punctured (step 9) and tethered electrode implanted rats (PT group); (iii) punctured and telemetry electrode implanted rats (PTe group). A total of 9 animals per group (6 epileptic and 3 control rats) were used. The number of successful collections over 5 times was evaluated. The success rate was similar in punctured rats: 86.7% &#177; 5.8% in tethered and 88.9% &#177; 4.8% in telemetry electrode implanted animals. Instead, in the cannulated rats, the rate was reduced even if not significantly different (71.1% &#177; 8.9%, Table 1). Such results indicate that the cannula on animals&#39; heads may interfere with repeated CSF sampling and compromise longitudinal studies. The puncture technique is more suitable for multiple CSF withdrawals in electrodes implanted animals.
Impact of vacuum and tail milking on the plasma collection method 
Blood was collected 5x from 9 rats (6 epileptic and 3 control rats) at days 52, 55, 58, 61, and 64 post-SE and the plasma quality was evaluated for hemolysis visually and by UV spectrophotometry at 414 nm. To obtain the first sample in each rat, the vacuum withdrawal via a 21G butterfly needle attached to a 1 mL syringe was employed. With the second sample, the drop withdrawal and 21G butterfly needle system were employed when milking the tail simultaneously. To get the 3rd-5th sample, the drop withdrawal procedure without milking the tail (described in step 9) was used.
When employing a vacuum, the plasma was pink colored under the visual inspection, and the mean absorbance value of 9 rats&#39; samples was 0.647 &#177; 0.067 (Table 2, Figure 3). Similar results were obtained if employing the tail milking during the procedure: pink-colored plasma with 0.620 &#177; 0.043 mean absorbance (Table 2, Figure 3). In contrast, with the gravity-enabled drop withdrawal and 21G butterfly needle system, the mean plasma absorbance values were significantly reduced (0.226 &#177; 0.017 at 58 dpSE; 0.223 &#177; -0.09 at 61 dpSE; 0.226 &#177; 0.018 at 64 dpSE; Table 2, Figure 3) with respect to vacuum or tail milking method. Moreover, the drop plasma samples were mainly transparent. Higher values of absorbance (52 and 55 dpSE) correlated with the pink color of samples (data not shown). These results may suggest that the last method is the best to get samples of very high quality for analyses.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/65636/65636fig01.jpg" /> 
Figure 1: Key steps of plasma sampling workflow. (A) Materials necessary for blood withdrawal and rat in the stereotaxic frame, ready for collection; (B, C) Magnifications of the tail with 21G butterfly needle inserted into the lateral tail vein and the blood drop falling down the walls of the collection tube with an anticoagulant. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65636/65636fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/65636/65636fig02.jpg" /> 
Figure 2: Key steps of cerebrospinal fluid (CSF) sampling workflow. (A) Materials necessary for the CSF withdrawal and rat in the stereotaxic frame, shortly before collection; (B) The 23G butterfly needle preparation by cutting its plastic sleeve protection so that the end of the bare needle is exposed for 7 mm to ensure correct penetration into the cisterna magna; (C) The rat head is inclined downwards by 45&#176; during withdrawal. (D) Magnification on the rhomboid site with a butterfly needle inserted in the cisterna magna. Note the CSF that rises in the tubing, indicated by the tip of the marker. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65636/65636fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/65636/65636fig03.jpg" /> 
Figure 3: Quality evaluation of plasma samples. Degree of hemolysis measured at 414 nm for free hemoglobin by UV spectroscopy in plasma samples of 9 animals at 5 time-points (52, 55, 58, 61, and 64 days&#39; post status epilepticus, dpSE) using different methods: day 52 - the vacuum technique; day 55 - the tail milking; days 58-64 the drop techniques were employed. The decrease in free hemoglobin in plasma obtained by drop technique compared to vacuum and tail milking methods was significant (*p &#60;0.05 according to one-way ANOVA and post-hoc Tukey&#39;s multiple comparison test). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65636/65636fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
Table 1: Success rates of CSF withdrawals. Comparison of the success rates of repeated CSF withdrawal in three experimental groups of animals expressed as a percentage of successful withdrawals across 5 days. The value 1 was assigned to successful withdrawal of &#62; 100 &#181;L of clear CSF; the zero value was assigned to withdrawals &#60; 100 &#181;L and/or of unclear CSF. Abbreviations: N/A - the absence of collection due to the loss of cannula during the sampling procedure (CT animals only); CT - cannulated tethered; PT - punctured tethered; PTe - punctured telemetry electrodes implanted. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65636/Table 1_Soukupova et al 2023_RE.xlsx" target="_blank">Please click here to download this Table.</a>
Table 2: Evaluation of hemolysis in plasma samples. Results of the hemolysis measurements at 5 time-points using three different methods of blood sampling: day 52 - the vacuum technique; day 55 - the tail milking; days 58-64 the drop techniques. Values &#62;0.3 of absorbance correlated with pink color of samples. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/65636/Table 2_Soukupova et al 2023_RE.xlsx" target="_blank">Please click here to download this Table.</a>

Watch this Scientific Journal Video about Obtaining High-Quality CSF and Blood Samples for Epilepsy Biomarker Discovery at JoVE.com

Author Spotlight: Obtaining High-Quality CSF and Blood Samples for Epilepsy Biomarker Discovery 

The protocol shows repeated cerebrospinal fluid and blood collections from epileptic rats performed in parallel with continuous video-electroencephalogram (EEG) monitoring. These are instrumental for exploring possible links between changes in various body fluid molecules and seizure activity.

Sampling Cerebrospinal Fluid and Blood from Lateral Tail Vein in Rats During EEG Recordings

Because the composition of body fluids reflects many physiological and pathological dynamics, biological liquid samples are commonly obtained in many ...

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2.6K Views.  Universita degli Studi di Ferrara. The protocol shows repeated cerebrospinal fluid and blood collections from epileptic rats performed in parallel with continuous video-electroencephalogram (EEG) monitoring. These are instrumental for exploring possible links between changes in various body fluid molecules and seizure activity. 

Video: Author Spotlight: Obtaining High-Quality CSF and Blood Samples for Epilepsy Biomarker Discovery 

High-density EEG Recordings of the Freely Moving Mice using Polyimide-based Microelectrode

Electroencephalogram (EEG) indicates the averaged electrical activity of the neuronal populations on a large-scale level. It is widely utilized as a noninvasive brain monitoring tool in cognitive neuroscience as well as a diagnostic tool for epilepsy and sleep disorders in neurology. However, the underlying mechanism of EEG rhythm generation is still under the veil. Recently introduced polyimide-based microelectrode (PBM-array) for high resolution mouse EEG1 is one of the trials to answer the neurophysiological questions on EEG signals based on a rich genetic resource that the mouse model contains for the analysis of complex EEG generation process. This application of nanofabricated PBM-array to mouse skull is an efficient tool for collecting large-scale brain activity of transgenic mice and accommodates to identify the neural correlates to certain EEG rhythms in conjunction with behavior. However its ultra-thin thickness and bifurcated structure cause a trouble in handling and implantation of PBM-array. In the presented video, the preparation and surgery steps for the implantation of PBM-array on a mouse skull are described step by step. Handling and surgery tips to help researchers succeed in implantation are also provided.

In this article, we described the surgery procedure and handling tips for implantation of ultra-thin polyimide-based microelectrode array (PBM-array) on the mouse skull for acquisition of high-density encephalography (EEG) in a mouse model.

Electroencephalogram (EEG) indicates the averaged electrical activity of the neuronal populations on a large-scale level. It is widely utilized as a ...

Lateral Fluid Percussion: Model of Traumatic Brain Injury in Mice

Traumatic brain injury (TBI) research has attained renewed momentum due to the increasing awareness of head injuries, which result in morbidity and mortality. Based on the nature of primary injury following TBI, complex and heterogeneous secondary consequences result, which are followed by regenerative processes 1,2. Primary injury can be induced by a direct contusion to the brain from skull fracture or from shearing and stretching of tissue causing displacement of brain due to movement 3,4. The resulting hematomas and lacerations cause a vascular response 3,5, and the morphological and functional damage of the white matter leads to diffuse axonal injury 6-8. Additional secondary changes commonly seen in the brain are edema and increased intracranial pressure 9. Following TBI there are microscopic alterations in biochemical and physiological pathways involving the release of excitotoxic neurotransmitters, immune mediators and oxygen radicals 10-12, which ultimately result in long-term neurological disabilities 13,14. Thus choosing appropriate animal models of TBI that present similar cellular and molecular events in human and rodent TBI is critical for studying the mechanisms underlying injury and repair.
Various experimental models of TBI have been developed to reproduce aspects of TBI observed in humans, among them three specific models are widely adapted for rodents: fluid percussion, cortical impact and weight drop/impact acceleration 1. The fluid percussion device produces an injury through a craniectomy by applying a brief fluid pressure pulse on to the intact dura. The pulse is created by a pendulum striking the piston of a reservoir of fluid. The percussion produces brief displacement and deformation of neural tissue 1,15. Conversely, cortical impact injury delivers mechanical energy to the intact dura via a rigid impactor under pneumatic pressure 16,17. The weight drop/impact model is characterized by the fall of a rod with a specific mass on the closed skull 18. Among the TBI models, LFP is the most established and commonly used model to evaluate mixed focal and diffuse brain injury 19. It is reproducible and is standardized to allow for the manipulation of injury parameters. LFP recapitulates injuries observed in humans, thus rendering it clinically relevant, and allows for exploration of novel therapeutics for clinical translation 20.
We describe the detailed protocol to perform LFP procedure in mice. The injury inflicted is mild to moderate, with brain regions such as cortex, hippocampus and corpus callosum being most vulnerable. Hippocampal and motor learning tasks are explored following LFP.

Lateral fluid percussion (LFP), an established model of traumatic brain injury in mice, is demonstrated. LFP fulfills three major criteria for animal models: validity, reliability and clinical relevance. The procedure, consisting of surgical craniotomy, fixation of hub followed by induction of injury, resulting in focal and diffuse injuries, is described.

Traumatic brain injury (TBI) research has attained renewed momentum due to the increasing awareness of head injuries, which result in morbidity and ...

The Tail Suspension Test

The tail-suspension test is a mouse behavioral test useful in the screening of potential antidepressant drugs, and assessing of other manipulations that are expected to affect depression related behaviors. Mice are suspended by their tails with tape, in such a position that it cannot escape or hold on to nearby surfaces. During this test, typically six minutes in duration, the resulting escape oriented behaviors are quantified. The tail-suspension test is a valuable tool in drug discovery for high-throughput screening of prospective antidepressant compounds. Here, we describe the details required for implementation of this test with additional emphasis on potential problems that may occur and how to avoid them. We also offer a solution to the tail climbing behavior, a common problem that renders this test useless in some mouse strains, such as the widely used C57BL/6. Specifically, we prevent tail climbing behaviors by passing mouse tails through a small plastic cylinder prior to suspension. Finally, we detail how to manually score the behaviors that are manifested in this test.

The tail-suspension test is validated as an experimental procedure to assess antidepressant efficacy of drug treatments in mice. Mice are suspended by their tails for six minutes and escape-related behaviors are assessed. We describe procedures used in conducting the tail suspension test.

The tail-suspension test is a mouse behavioral test useful in the screening of potential antidepressant drugs, and assessing of other manipulations that ...

Isolation of Cerebrospinal Fluid from Rodent Embryos for use with Dissected Cerebral Cortical Explants

The CSF is a complex fluid with a dynamically varying proteome throughout development and in adulthood. During embryonic development, the nascent CSF differentiates from the amniotic fluid upon closure of the anterior neural tube. CSF volume then increases over subsequent days as the neuroepithelial progenitor cells lining the ventricles and the choroid plexus generate CSF. The embryonic CSF contacts the apical, ventricular surface of the neural stem cells of the developing brain and spinal cord. CSF provides crucial fluid pressure for the expansion of the developing brain and distributes important growth promoting factors to neural progenitor cells in a temporally-specific manner. To investigate the function of the CSF, it is important to isolate pure samples of embryonic CSF without contamination from blood or the developing telencephalic tissue. Here, we describe a technique to isolate relatively pure samples of ventricular embryonic CSF that can be used for a wide range of experimental assays including mass spectrometry, protein electrophoresis, and cell and primary explant culture. We demonstrate how to dissect and culture cortical explants on porous polycarbonate membranes in order to grow developing cortical tissue with reduced volumes of media or CSF. With this method, experiments can be performed using CSF from varying ages or conditions to investigate the biological activity of the CSF proteome on target cells.

The ventricular cerebrospinal fluid (CSF) bathes the neuroepithelial and cerebral cortical progenitor cells during early brain development in the embryo. Here we describe the method developed to isolate ventricular CSF from rodent embryos of different ages in order to investigate its biological function. In addition, we demonstrate our cerebral cortical explant dissection and culture technique that allows for explant growth with minimal volumes of culture medium or CSF.

The CSF is a complex fluid with a dynamically varying proteome throughout development and in adulthood. During embryonic development, the nascent CSF ...

Extracting Visual Evoked Potentials from EEG Data Recorded During fMRI-guided Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator&#39;s coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes.

This paper describes a method for collecting and analyzing electroencephalography (EEG) data during concurrent transcranial magnetic stimulation (TMS) guided by activations revealed with functional magnetic resonance imaging (fMRI). A method for TMS artifact removal and extraction of event related potentials is described as well as considerations in paradigm design and experimental setup.

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological ...

Recording EEG in Freely Moving Neonatal Rats Using a Novel Method

EEG is a useful method to detect electrical activity in the brain. Moreover, it is a widely used diagnostic tool for various neurological conditions, such as epilepsy and neurodegenerative disorders. However, it is technically difficult to obtain EEG recordings in neonates as it requires specialized handling and great care. Here, we present a novel method to record EEG in neonatal rat pups (P8-P15). We designed a simple and reliable electrode using computer pin loci; it can be easily implanted into the skull of a rat pup to record high-quality EEG signals in the normal and epileptic brain. Pups were given an intraperitoneal (i.p.) injection of the neurotoxin kainic acid (KA) to induce epileptic seizures. The surgical implantation performed in this procedure is less expensive than other EEG procedures for neonates. This method allows one to record high-quality and stable EEG signals for more than 1 week. Furthermore, this procedure can also be applied to adult rats and mice to study epilepsy or other neurological disorders.

Here, we introduce a novel technique designed to record electroencephalography (EEG) in freely moving neonatal epileptic pups and describe its procedures, features, and applications. This method allows one to record EEG for more than 1 week.

EEG is a useful method to detect electrical activity in the brain. Moreover, it is a widely used diagnostic tool for various neurological conditions, such ...

Sample Preparation for Endopeptidomic Analysis in Human Cerebrospinal Fluid

This protocol describes a method developed to identify endogenous peptides in human cerebrospinal fluid (CSF). For this purpose, a previously developed method based on molecular weight cut-off (MWCO) filtration and mass spectrometric analysis was combined with an offline high-pH reverse phase HPLC pre-fractionation step.
Secretion into CSF is the main pathway for removal of molecules shed by cells of the central nervous system. Thus, many processes in the central nervous system are reflected in the CSF, rendering it a valuable diagnostic fluid. CSF has a complex composition, containing proteins that span a concentration range of 8 - 9 orders of magnitude. Besides proteins, previous studies have also demonstrated the presence of a large number of endogenous peptides. While less extensively studied than proteins, these may also hold potential interest as biomarkers.
Endogenous peptides were separated from the CSF protein content through MWCO filtration. By removing a majority of the protein content from the sample, it is possible to increase the sample volume studied and thereby also the total amount of the endogenous peptides. The complexity of the filtrated peptide mixture was addressed by including a reverse phase (RP) HPLC pre-fractionation step at alkaline pH prior to LC-MS analysis. The fractionation was combined with a simple concatenation scheme where 60 fractions were pooled into 12, analysis time consumption could thereby be reduced while still largely avoiding co-elution.
Automated peptide identification was performed by using three different peptide/protein identification software programs and subsequently combining the results. The different programs were complementary rather than comparable with less than 15% of the identifications overlapped between the three.

A method for mass spectrometric analysis of endogenous peptides in human cerebrospinal fluid (CSF) is presented. By employing molecular weight cut-off filtration, chromatographic pre-fractionation, mass spectrometric analysis and a subsequent combination of peptide identification strategies, it was possible to expand the known CSF peptidome nearly ten-fold compared to previous studies.

This protocol describes a method developed to identify endogenous peptides in human cerebrospinal fluid (CSF). For this purpose, a previously developed ...

An Improved Method for Collection of Cerebrospinal Fluid from Anesthetized Mice

The cerebrospinal fluid (CSF) is a valuable body fluid for analysis in neuroscience research. It is one of the fluids in closest contact with the central nervous system and thus, can be used to analyze the diseased state of the brain or spinal cord without directly accessing these tissues. However, in mice it is difficult to obtain from the cisterna magna due to its closeness to blood vessels, which often contaminate samples. The area for CSF collection in mice is also difficult to dissect to and often only small samples are obtained (maximum of 5-7 &#181;L or less). This protocol describes in detail a technique that improves on current methods of collection to minimize contamination from blood and allow for the abundant collection of CSF (on average 10-15 &#181;L can be collected). This technique can be used with other dissection methods for tissue collection from mice, as it does not impact any tissues during CSF extraction. Thus, the brain and spinal cord are not affected with this technique and remain intact. With greater CSF sample collection and purity, more analyses can be used with this fluid to further aid neuroscience research and better understand diseases affecting the brain and spinal cord.

This protocol describes an improved technique for the abundant collection of cerebrospinal fluid (CSF) with no contamination from blood. With greater sample collection and purity, more analyses can be performed using CSF to further our understanding of diseases that affect the brain and spinal cord.

The cerebrospinal fluid (CSF) is a valuable body fluid for analysis in neuroscience research. It is one of the fluids in closest contact with the central ...

Visual Evoked Potential Recordings in Mice Using a Dry Non-invasive Multi-channel Scalp EEG Sensor

For scalp EEG research environments with laboratory mice, we designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable because of the plunger-spring-barrel structural facet and mechanical strengths resulting from metal materials. The whole process for acquiring the VEP responses in vivo from a mouse consists of four steps: (1) sensor assembly, (2) animal preparation, (3) VEP measurement, and (4) signal processing. This paper presents representative measurements of VEP responses from multiple mice with a submicro-voltage signal resolution and sub-hundred millisecond temporal resolution. Although the proposed method is safer and more convenient compared to other previously reported animal EEG acquiring methods, there are remaining issues including how to enhance the signal-to-noise ratio and how to apply this technique with freely moving animals. The proposed method utilizes easily available resources and shows a repetitive VEP response with a satisfactory signal quality. Therefore, this method could be utilized for longitudinal experimental studies and reliable translational research exploiting non-invasive paradigms.

We designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable. This paper describes the whole process from manufacturing the proposed EEG electrode to signal processing of visual evoked potential (VEP) signals measured on a mouse scalp using a dry non-invasive multi-channel EEG sensor.

For scalp EEG research environments with laboratory mice, we designed a dry-type 16 channel EEG sensor which is non-invasive, deformable, and re-usable ...

Frequent Tail-tip Blood Sampling in Mice for the Assessment of Pulsatile Luteinizing Hormone Secretion

In many endocrine systems, circulating factors or hormones are not released continuously, but are secreted as a discrete pulse in response to a releasing factor. Single-point sampling measures are inadequate to fully understand the biological significance of the secretory pattern of pulsatile hormones either under normal physiologic conditions or during conditions of dysregulation. Luteinizing hormone (LH) is synthesized by the anterior pituitary gonadotrope&#160;cells and secreted in a pulsatile pattern which requires frequent collection of blood samples for pulse assessment. This has not been possible in mice until recently, due to the development of a high-sensitivity LH assay and advancement in a technique for frequent low-volume sample collection, initially described by Steyn and colleagues.1 Here we describe a protocol for the frequent peripheral blood sample collection from mice with sufficient handling acclimatization to detect pulsatile secretion of LH. The current protocol details an expanded acclimatization period that allows assessment of robust and continuous pulses of LH over multiple hours. In this protocol, the tip of the tail is clipped&#160;and blood is collected from the tail using a hand-held pipette. For assessment of pulsatile LH in gonadectomized mice, serial samples are collected every 5-6 min for 90-180 min. Importantly, the collection of blood and measurement of robust pulses of LH can be accomplished in awake, freely behaving mice, given adequate handling acclimatization and effort to minimize environmental stressors. Sufficient acclimatization can be achieved within 4-5 weeks prior to blood collection. This protocol highlights advances in the methodology to ensure collection of whole blood samples for assessment of pulsatile LH secretion patterns over multiple hours in the mouse, a powerful animal model for neuroendocrine research.

Here we present a tail-tip blood sampling protocol for frequent sample collection in unrestrained mice. This method is useful for assessing patterns of pulsatile luteinizing hormone secretion and could be adapted for analysis of other circulating factors.

In many endocrine systems, circulating factors or hormones are not released continuously, but are secreted as a discrete pulse in response to a releasing ...