This work was supported by the J.B. Marshall Foundation.

1. Prepare Animal and Equipment for Procedure
<ol>
	<li>Before beginning surgery, prepare the surgical area and the animal. Make the carotid catheter by inserting a 23-gauge blunt needle into one end of 12" of PE50 tubing. Cut an approximately 45&deg; bevel in the opposite end of the catheter. Sterilize equipment prior to the procedure. Wear a hair bonnet, surgical mask, and sterile gloves.</li>
	<li>Place a heating pad on the surface where the surgery will be performed. Activate it and allow it to warm. Cover the area with an absorbent bench pad.</li>
	<li>Verify that you have 25% mannitol in solution without crystals. If crystals are present, dissolve them by placing the vial in a hot water bath at 80 &deg;C and agitating periodically.</li>
	<li>Record the mass of the animal.</li>
	<li>Make a propofol dilution for delivery at 0.8 mg/kg/min at a rate of 0.1 ml/min.</li>
	<li>Place the rat in the induction box for 3 min. Settings: 5% isoflurane, 2 L/min flow rate on ventilator.</li>
	<li>On top of a disposable towel, shave the neck and both inner thighs.</li>
</ol>
2. Intubate the Rat
<ol>
	<li>Place the animal back in the induction box for 3 min.</li>
	<li>Prepare your endotracheal tube with an IV catheter. For this size and strain of rat, we use an 18 ga catheter. The tube must be large enough to allow adequate airflow, but small enough to fit into the trachea without causing damage. Pull the needle out of the plastic catheter and carefully break the needle approx. 1 cm from its sharp tip. The bunted needle will be your stylus. Put the needle back into the catheter.</li>
	<li>Hang the rat by its teeth on an angled surface.</li>
	<li>Shine a light directly against the animal's neck and lined up between its ears.</li>
	<li>Insert a small spatula approx. 3 cm into the oropharynx. Lift upward while gently pulling the tongue out of the mouth.</li>
	<li>Visualize the opening of the trachea. You will see a small hole open and close with each breath.</li>
	<li>Gently insert catheter into the hole. You can sometimes feel the plastic enter the cartilage of the trachea. The trachea is sensitive. Do not force the catheter.</li>
	<li>Set the ventilator to 1 L/min and 60 bpm and the isoflurane to 2%.</li>
	<li>Connect the catheter to the ventilator and tape the tube to the operating surface.</li>
	<li>Verify the animal is anesthetized by performing a toe pinch.</li>
</ol>
3. Establish Propofol IV Anesthesia
<ol>
	<li>Secure the rat by taping all four limbs and the tail to the operating surface.</li>
	<li>Scrub the shaved neck and groin sites with chlorhexidine soap three times. Then scrub with chlorhexidine rinse three times.</li>
	<li>Attach a syringe of propofol to an IV extension set. Mount the syringe on an infusion pump.</li>
	<li>Using a scalpel, cut through the skin of the shaved thigh. Avoid cutting muscle.</li>
	<li>Open the incision with forceps to visualize the femoral vein.</li>
	<li>Pull away tissue over the artery to expose the vessel.</li>
	<li>Insert a 26 ga monoject veterinary IV catheter into vein. When the needle punctures the wall of the vein you will feel it become easier to push. Retract the needle and push the catheter into the vessel.</li>
	<li>Start the propofol infusion at 0.1 ml/min.</li>
	<li>3-5 min after beginning the propofol infusion, switch the anesthesia gas to a mixture of 50% O2 and 50% N2O and shut off the isoflurane.</li>
</ol>
4. Expose the Bifurcation of the Common Carotid Artery
<ol>
	<li>Make a midline incision at the neck with scalpel blade.</li>
	<li>Cut between the two large salivary glands with scissors or scalpel.</li>
	<li>Dissect away tissue lateral to the midline to expose the carotid artery. Use forceps to open layers of tissue. You can use scissors to remove pieces that you expose with the forceps and determine to be minimally vascular. Control bleeding with gauze, cotton swabs, and cautery if necessary.</li>
	<li>Inject 3 ml saline IP if there has been moderate to heavy bleeding.</li>
	<li>Use retractors to pull tissue away from the carotid. Find the bifurcation.</li>
	<li>Expose the occipital artery just distal to the bifurcation. Cauterize it between forceps and separate it with an electrocautery.</li>
	<li>Use forceps to fully expose the carotid bifurcation and as much of the ECA as possible.</li>
	<li>Expose the superior thyroid artery branching off the ECA distal to the occipital artery. Cauterize it between forceps and separate it with an electrocautery.</li>
</ol>
5. Catheterize the External Carotid Artery
<ol>
	<li>Place 2 lengths of 4/0 silk under the ECA.</li>
	<li>Grab 1 length of suture with your hemostat and retract the ECA back caudally (toward the rat's feet).</li>
	<li>Take the other suture and tie as far cranially (toward the rat's mouth) as possible with a surgeon's knot. This forms a permanent ligature to sacrifice the ECA.</li>
	<li>Remove the first hemostat (the one that was applying caudal tension) and grab the other suture (the one that is knotted around the ECA) and apply gentle tension cranially with the hemostat.</li>
	<li>Tie another surgeon's knot loosely (do not secure - leave barely tied) distal to the bifurcation and proximal to the permanent ligature.</li>
	<li>Irrigate with 1% lidocaine to relax the artery.</li>
	<li>Fill your catheter with heparinized saline.</li>
	<li>Place a temporary vessel clip as close as possible to the bifurcation. Place vessel clip at an angle to maximize space for catheterization. Slide the loose knot toward the clip.</li>
	<li>Make a small arteriotomy (cut) in ECA just proximal to the ligature using microscissors. There should be no bleeding if the clip and ligature are secure.</li>
	<li>Using forceps to control the ECA walls, feed the beveled end of the catheter into the vessel.</li>
	<li>Secure the catheter with the loose suture knot. Tie the artery around the catheter.</li>
	<li>Remove the clip and clean the area with a cotton swab.</li>
	<li>Advance the catheter to about 1 mm distal to bifurcation. Hold the artery with forceps proximal to the knot to ensure the vessel is immobilized.</li>
</ol>
6. Administer Mannitol
<ol>
	<li>Fill an 8" IV extension set and a 6 ml syringe with mannitol without creating any air bubbles. Store this in the incubator at 37 &deg;C. Note: work quickly with mannitol - it will readily precipitate out of solution at room temperature.</li>
	<li>In order to visualize BBBD, you may administer Evans blue dye and watch it enter the areas of the brain where the barrier has been disrupted. To do this, give the animal 2 ml/kg of 2% Evans Blue through a new IV site on leg contralateral to the propofol infusion.</li>
	<li>Attach the extension set to a 5 &mu;m filter and fill it with mannitol to remove air bubbles. Then, attach this to the stopcock without creating bubbles.</li>
	<li>Administer mannitol at 0.09 ml/sec for 25 sec. Watch for the mannitol to reach equilibrium with the flow in common carotid at a point just proximal to the ICA. It should appear to pulse with the rat's heart rate. If the mannitol simply flows down toward the heart you have overcome the rat's blood pressure. This can cause life-threatening complications and poor BBBD.</li>
</ol>

<ol>
	<li>Abbott, N. J., Patabendige, A. A. K., Dolman, D. E. M., Yusof, S. R., Begley, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structure+and+function+of+the+blood-brain+barrier.">Structure and function of the blood-brain barrier.</a> Neurobiology of disease. 37, 13-25 (2010).</li><li>Smith, Q. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Blood-Brain+Barrier.">The Blood-Brain Barrier.</a> 89, 193-208 (2003).</li><li>Kroll, R. A., Neuwelt, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Outwitting+the+blood-brain+barrier+for+therapeutic+purposes:+osmotic+opening+and+other+means.">Outwitting the blood-brain barrier for therapeutic purposes: osmotic opening and other means.</a> Neurosurgery. 42, 1083 (1998).</li><li>Kroll, R. A., Pagel, M. A., Muldoon, L. L., Roman-Goldstein, S., Neuwelt, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increasing+volume+of+distribution+to+the+brain+with+interstitial+infusion:+dose,+rather+than+convection,+might+be+the+most+important+factor.">Increasing volume of distribution to the brain with interstitial infusion: dose, rather than convection, might be the most important factor.</a> Neurosurgery. 38, 746-754 (1996).</li><li>Butt, A. M., Jones, H. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+histamine+and+antagonists+on+electrical+resistance+across+the+blood-brain+barrier+in+rat+brain-surface+microvessels.">Effect of histamine and antagonists on electrical resistance across the blood-brain barrier in rat brain-surface microvessels.</a> Brain research. 569, 100-105 (1992).</li><li>Inamura, T., Black, K. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bradykinin+selectively+opens+blood-tumor+barrier+in+experimental+brain+tumors.">Bradykinin selectively opens blood-tumor barrier in experimental brain tumors.</a> Journal of Cerebral Blood Flow &amp; Metabolism. 14, 862-870 (1994).</li><li>Matsukado, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+tumor+uptake+of+carboplatin+and+survival+in+glioma-bearing+rats+by+intracarotid+infusion+of+bradykinin+analog,+RMP-7.">Enhanced tumor uptake of carboplatin and survival in glioma-bearing rats by intracarotid infusion of bradykinin analog, RMP-7.</a> Neurosurgery. 39, 125 (1996).</li><li>Kroll, R. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improving+drug+delivery+to+intracerebral+tumor+and+surrounding+brain+in+a+rodent+model:+a+comparison+of+osmotic+versus+bradykinin+modification+of+the+blood-brain+and/or+blood-tumor+barriers.">Improving drug delivery to intracerebral tumor and surrounding brain in a rodent model: a comparison of osmotic versus bradykinin modification of the blood-brain and/or blood-tumor barriers.</a> Neurosurgery. 43, 879 (1998).</li><li>Kinoshita, M., McDannold, N., Jolesz, F. A., Hynynen, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Noninvasive+localized+delivery+of+Herceptin+to+the+mouse+brain+by+MRI-guided+focused+ultrasound-induced+blood-brain+barrier+disruption.">Noninvasive localized delivery of Herceptin to the mouse brain by MRI-guided focused ultrasound-induced blood-brain barrier disruption.</a> Proceedings of the National Academy of Sciences. 103, 11719-11723 (2006).</li><li>Neuwelt, E. A., Dahlborg, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chemotherapy+administered+in+conjunction+with+osmotic+blood-brain+barrier+modification+in+patients+with+brain+metastases.">Chemotherapy administered in conjunction with osmotic blood-brain barrier modification in patients with brain metastases.</a> Journal of neuro-oncology. 4, 195-207 (1987).</li><li>Doolittle, N. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safety+and+efficacy+of+a+multicenter+study+using+intraarterial+chemotherapy+in+conjunction+with+osmotic+opening+of+the+blood-brain+barrier+for+the+treatment+of+patients+with+malignant+brain+tumors.">Safety and efficacy of a multicenter study using intraarterial chemotherapy in conjunction with osmotic opening of the blood-brain barrier for the treatment of patients with malignant brain tumors.</a> Cancer. 88, 637-647 (2000).</li><li>Guillaume, D. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intra-arterial+chemotherapy+with+osmotic+blood-brain+barrier+disruption+for+aggressive+oligodendroglial+tumors:+results+of+a+phase+I+study.">Intra-arterial chemotherapy with osmotic blood-brain barrier disruption for aggressive oligodendroglial tumors: results of a phase I study.</a> Neurosurgery. 66, 48 (2010).</li><li>Remsen, L. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+anesthetic+choice,+PaCO2,+and+other+factors+on+osmotic+blood-brain+barrier+disruption+in+rats+with+brain+tumor+xenografts.">The influence of anesthetic choice, PaCO2, and other factors on osmotic blood-brain barrier disruption in rats with brain tumor xenografts.</a> Anesthesia &amp; Analgesia. 88, 559-559 (1999).</li><li>Nilaver, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Delivery+of+herpesvirus+and+adenovirus+to+nude+rat+intracerebral+tumors+after+osmotic+blood-brain+barrier+disruption.">Delivery of herpesvirus and adenovirus to nude rat intracerebral tumors after osmotic blood-brain barrier disruption.</a> Proceedings of the National Academy of Sciences. 92, 9829 (1995).</li><li>Fortin, D., McCormick, C. I., Remsen, L. G., Nixon, R., Neuwelt, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Unexpected+neurotoxicity+of+etoposide+phosphate+administered+in+combination+with+other+chemotherapeutic+agents+after+blood-brain+barrier+modification+to+enhance+delivery,+using+propofol+for+general+anesthesia,+in+a+rat+model.">Unexpected neurotoxicity of etoposide phosphate administered in combination with other chemotherapeutic agents after blood-brain barrier modification to enhance delivery, using propofol for general anesthesia, in a rat model.</a> Neurosurgery. 47, 199 (2000).</li><li>Neuwelt, E. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Primary+CNS+lymphoma+treated+with+osmotic+blood-brain+barrier+disruption:+prolonged+survival+and+preservation+of+cognitive+function.">Primary CNS lymphoma treated with osmotic blood-brain barrier disruption: prolonged survival and preservation of cognitive function.</a> Journal of clinical oncology. 9, 1580 (1991).</li><li>Remsen, L. G., Trail, P. A., Hellstr&#246;m, I., Hellstr&#246;m, K. E., Neuwelt, E. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+delivery+improves+the+efficacy+of+a+tumor-specific+doxorubicin+immunoconjugate+in+a+human+brain+tumor+xenograft+model.">Enhanced delivery improves the efficacy of a tumor-specific doxorubicin immunoconjugate in a human brain tumor xenograft model.</a> Neurosurgery. 46, 704 (2000).</li><li>Neuwelt, E. A., Pagel, M. A., Kraemer, D. F., Peterson, D. R., Muldoon, L. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bone+marrow+chemoprotection+without+compromise+of+chemotherapy+efficacy+in+a+rat+brain+tumor+model.">Bone marrow chemoprotection without compromise of chemotherapy efficacy in a rat brain tumor model.</a> Journal of Pharmacology and Experimental Therapeutics. 309, 594-599 (2004).</li></ol>

No conflicts of interest declared.

There are a few means of maximizing the efficacy of BBBD. It is important to minimize bleeding during the cut-down phase. Blood pressure and heart rate can be affected by substantial bleeding and these factors are known to affect the degree of BBBD13. Bleeding can be reduced by using sutures to ligate major vessels, such as the superior thyroid and occipital arteries, which must be divided. Additionally, electrocautery can be used to divide vessels and dissect areas that have a rich blood supply. It is also important to keep air and solids out of all lines placed into the animal - particularly the carotid catheter. Working quickly with the mannitol helps to ensure that crystals do not form inside the syringe or tubing.
It is important to use a mannitol flow rate that is effective for the size and strain of rat used in this experiment. The flow rate of the mannitol infusion must match the pressure in the rat's common carotid artery such that a high concentration of mannitol flows into the ICA without flowing down the common carotid into the heart and lungs, which can cause damage. Researchers choosing a different size and strain of rat than the one used in this study should conduct experiments to find the correct mannitol flow rate.
One of the limitations of this procedure is that it requires the sacrifice of the ECA. Once the ECA is catheterized, it becomes difficult and unreliable to catheterize again. Thus, this procedure cannot be performed twice on the same hemisphere. Additionally, compounds given following BBBD must be carefully tested for neurotoxicity. Some drugs that are ordinarily safe become dangerous once they cross the blood-brain barrier.
Despite these limitations, BBBD has been used extensively to study improved delivery of chemotherapy to brain tumors8,15-18. It may also be useful for other therapeutic applications in which a drug does not effectively cross the blood-brain barrier and administering mannitol is known to be safe.

<table border="1">
 <tbody>
 <tr>
 <td>Material Name</td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comment</td>
 </tr>
 <tr>
 <td>Long Evans rat</td>
 <td>Harlan Laboratories</td>
 <td></td>
 <td>210-250 g, male</td>
 </tr>
 <tr>
 <td>PE 50 Tubing</td>
 <td>Beckton-Dickinson</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>18 gauge x 2.5" IV catheter</td>
 <td>Terumo</td>
 <td></td>
 <td>For ET tube</td>
 </tr>
 <tr>
 <td>30" IV extension sets</td>
 <td>Abbott</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>26 gauge veterinary IV catheter</td>
 <td>Monoject</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Evans blue dye</td>
 <td>Sigma</td>
 <td>E2129</td>
 <td></td>
 </tr>
 <tr>
 <td>Bipolar</td>
 <td>Codman</td>
 <td></td>
 <td></td>
 </tr>
 <tr>
 <td>Filter, 5 &mu;m</td>
 <td>Braun</td>
 <td></td>
 <td></td>
 </tr>
 </tbody>
 </table>

rat model of blood-brain barrier disruption to allow targeted neurovascular therapeutics

Endothelial cells with tight junctions along with the basement membrane and astrocyte end feet surround cerebral blood vessels to form the blood-brain barrier1. The barrier selectively excludes molecules from crossing between the blood and the brain based upon their size and charge. This function can impede the delivery of therapeutics for neurological disorders. A number of chemotherapeutic drugs, for example, will not effectively cross the blood-brain barrier to reach tumor cells2. Thus, improving the delivery of drugs across the blood-brain barrier is an area of interest.
The most prevalent methods for enhancing the delivery of drugs to the brain are direct cerebral infusion and blood-brain barrier disruption3. Direct intracerebral infusion guarantees that therapies reach the brain; however, this method has a limited ability to disperse the drug4. Blood-brain barrier disruption (BBBD) allows drugs to flow directly from the circulatory system into the brain and thus more effectively reach dispersed tumor cells. Three methods of barrier disruption include osmotic barrier disruption, pharmacological barrier disruption, and focused ultrasound with microbubbles. Osmotic disruption, pioneered by Neuwelt, uses a hypertonic solution of 25% mannitol that dehydrates the cells of the blood-brain barrier causing them to shrink and disrupt their tight junctions. Barrier disruption can also be accomplished pharmacologically with vasoactive compounds such as histamine5 and bradykinin6. This method, however, is selective primarily for the brain-tumor barrier7. Additionally, RMP-7, an analog of the peptide bradykinin, was found to be inferior when compared head-to-head with osmotic BBBD with 25% mannitol8. Another method, focused ultrasound (FUS) in conjunction with microbubble ultrasound contrast agents, has also been shown to reversibly open the blood-brain barrier9. In comparison to FUS, though, 25% mannitol has a longer history of safety in human patients that makes it a proven tool for translational research10-12.
In order to accomplish BBBD, mannitol must be delivered at a high rate directly into the brain's arterial circulation. In humans, an endovascular catheter is guided to the brain where rapid, direct flow can be accomplished. This protocol models human BBBD as closely as possible. Following a cut-down to the bifurcation of the common carotid artery, a catheter is inserted retrograde into the ECA and used to deliver mannitol directly into the internal carotid artery (ICA) circulation. Propofol and N2O anesthesia are used for their ability to maximize the effectiveness of barrier disruption13. If executed properly, this procedure has the ability to safely, effectively, and reversibly open the blood-brain barrier and improve the delivery of drugs that do not ordinarily reach the brain 8,13,14.

<img alt="Figure 1" src="/files/ftp_upload/50019/50019fig1.jpg" /> 
Figure 1. Visualizing blood-brain barrier disruption via Evans blue dye extravasation. Evans blue dye is a pigment that binds to albumin and is not extravasated into the brain under physiological conditions. Disruption of the blood-brain barrier on one side of the brain allows Evans blue to enter and stain the disrupted hemisphere blue while the non-disrupted hemisphere remains unchanged. Thus, it is a useful marker of blood-brain barrier disruption. Figure 1A is an example of a brain without blood-brain barrier disruption. Figure 1B is an example of a brain stained blue after osmotic BBBD using 25% mannitol. Note that one hemisphere is stained blue while the other remains unstained. Some blue has entered the left hemisphere near the medial longitudinal fissure as a result of mixing of blood flow at the Circle of Willis.

Watch this Scientific Journal Video about Rat Model of Blood-brain Barrier Disruption to Allow Targeted Neurovascular Therapeutics at JoVE.com

Rat Model of Blood-brain Barrier Disruption to Allow Targeted Neurovascular Therapeutics

Blood-brain barrier disruption aids the delivery of certain drugs to the brain. Mannitol delivered intra-arterially shrinks cells surrounding blood vessels in order to physically disrupt the barrier.

Endothelial cells with tight junctions along with the basement membrane and astrocyte end feet surround cerebral blood vessels to form the blood-brain ...

rat-model-blood-brain-barrier-disruption-to-allow-targeted

Nanyang Technological University

Research

JoVE Journal

Medicine

19.3K Views.  Vanderbilt University School of Medicine. Blood-brain barrier disruption aids the delivery of certain drugs to the brain. Mannitol delivered intra-arterially shrinks cells surrounding blood vessels in order to physically disrupt the barrier.

Video: Rat Model of Blood-brain Barrier Disruption to Allow Targeted Neurovascular Therapeutics

MRI-guided Disruption of the Blood-brain Barrier using Transcranial Focused Ultrasound in a Rat Model

Focused ultrasound (FUS) disruption of the blood-brain barrier (BBB) is an increasingly investigated technique for circumventing the BBB1-5. The BBB is a significant obstacle to pharmaceutical treatments of brain disorders as it limits the passage of molecules from the vasculature into the brain tissue to molecules less than approximately 500 Da in size6. FUS induced BBB disruption (BBBD) is temporary and reversible4 and has an advantage over chemical means of inducing BBBD by being highly localized. FUS induced BBBD provides a means for investigating the effects of a wide range of therapeutic agents on the brain, which would not otherwise be deliverable to the tissue in sufficient concentration. While a wide range of ultrasound parameters have proven successful at disrupting the BBB2,5,7, there are several critical steps in the experimental procedure to ensure successful disruption with accurate targeting. This protocol outlines how to achieve MRI-guided FUS induced BBBD in a rat model, with a focus on the critical animal preparation and microbubble handling steps of the experiment.

Microbubble-mediated focused ultrasound disruption of the blood-brain barrier (BBB) is a promising technique for non-invasive targeted drug delivery in the brain1-3. This protocol outlines the experimental procedure for MRI-guided transcranial BBB disruption in a rat model.

Focused ultrasound (FUS) disruption of the blood-brain barrier (BBB) is an increasingly investigated technique for circumventing the BBB1-5. The BBB is a ...

Intranasal Administration of CNS Therapeutics to Awake Mice

Intranasal administration is a method of delivering therapeutic agents to the central nervous system (CNS). It is non-invasive and allows large molecules that do not cross the blood-brain barrier access to the CNS. Drugs are directly targeted to the CNS with intranasal delivery, reducing systemic exposure and thus unwanted systemic side effects1. Delivery from the nose to the CNS occurs within minutes along both the olfactory and trigeminal neural pathways via an extracellular route and does not require drug to bind to any receptor or axonal transport2. Intranasal delivery is a widely publicized method and is currently being used in human clinical trials3.
Intranasal delivery of drugs in animal models allows for initial evaluation of pharmacokinetic distribution and efficacy. With mice, it is possible to administer drugs to awake (non-anesthetized) animals on a regular basis using a specialized intranasal grip. Awake delivery is beneficial because it allows for long-term chronic dosing without anesthesia, it takes less time than with anesthesia, and can be learned and done by many people so that teams of technicians can dose large numbers of mice in short periods. Efficacy of therapeutics administered intranasally in this way to mice has been demonstrated in a number of studies including insulin in diabetic mouse models 4-6 and deferoxamine in Alzheimer's mouse models. 7,8
The intranasal grip for mice can be learned, but is not easy and requires practice, skill, and a precise grip to effectively deliver drug to the brain and avoid drainage to the lung and stomach. Mice are restrained by hand using a modified scruff in the non-dominant hand with the neck held parallel to the floor, while drug is delivered with a pipettor using the dominant hand. It usually takes 3-4 weeks of acclimating to handling before mice can be held with this grip without a stress response. We have prepared this JoVE video to make this intranasal delivery technique more accessible.

A method to intranasally administer drugs to awake mice for the purpose of targeting the brain is described. This method allows for repeat dosing over long periods using intranasal administration of drug without anesthesia, and nose-to-brain delivery with minimal systemic exposure.

Intranasal administration is a method of delivering  therapeutic agents to the central nervous system (CNS). It is  non-invasive and allows large ...

Stretch in Brain Microvascular Endothelial Cells (cEND) as an In Vitro Traumatic Brain Injury Model of the Blood Brain Barrier

Due to the high mortality incident brought about by traumatic brain injury (TBI), methods that would enable one to better understand the underlying mechanisms involved in it are useful for treatment. There are both in vivo and in vitro methods available for this purpose. In vivo models can mimic actual head injury as it occurs during TBI. However, in vivo techniques may not be exploited for studies at the cell physiology level. Hence, in vitro methods are more advantageous for this purpose since they provide easier access to the cells and the extracellular environment for manipulation.
Our protocol presents an in vitro model of TBI using stretch injury in brain microvascular endothelial cells. It utilizes pressure applied to the cells cultured in flexible-bottomed wells. The pressure applied may easily be controlled and can produce injury that ranges from low to severe. The murine brain microvascular endothelial cells (cEND) generated in our laboratory is a well-suited model for the blood brain barrier (BBB) thus providing an advantage to other systems that employ a similar technique. In addition, due to the simplicity of the method, experimental set-ups are easily duplicated. Thus, this model can be used in studying the cellular and molecular mechanisms involved in TBI at the BBB.

Stretch in Brain Microvascular Endothelial Cells cEND as an In Vitro Traumatic Brain Injury Model of the Blood Brain Barrier

In vitro traumatic brain injury models are being developed to reproduce in vivo brain deformation. Stretch-induced injury has been employed for astrocytes, neurons, glial cells, aortic, and brain endothelial cells. However, our system uses a blood brain barrier (BBB) model that possesses properties constituting a legitimate model of the BBB to establish an in vitro&#160;TBI model.

Due to the high mortality incident brought about by traumatic brain injury (TBI), methods that would enable one to better understand the underlying ...

Setting-up an In Vitro Model of Rat Blood-brain Barrier (BBB): A Focus on BBB Impermeability and Receptor-mediated Transport

The blood brain barrier (BBB) specifically regulates molecular and cellular flux between the blood and the nervous tissue. Our aim was to develop and characterize a highly reproducible rat syngeneic in vitro model of the BBB using co-cultures of primary rat brain endothelial cells (RBEC) and astrocytes to study receptors involved in transcytosis across the endothelial cell monolayer. Astrocytes were isolated by mechanical dissection following trypsin digestion and were frozen for later co-culture. RBEC were isolated from 5-week-old rat cortices. The brains were cleaned of meninges and white matter, and mechanically dissociated following enzymatic digestion. Thereafter, the tissue homogenate was centrifuged in bovine serum albumin to separate vessel fragments from nervous tissue. The vessel fragments underwent a second enzymatic digestion to free endothelial cells from their extracellular matrix. The remaining contaminating cells such as pericytes were further eliminated by plating the microvessel fragments in puromycin-containing medium. They were then passaged onto filters for co-culture with astrocytes grown on the bottom of the wells. RBEC expressed high levels of tight junction (TJ) proteins such as occludin, claudin-5 and ZO-1 with a typical localization at the cell borders. The transendothelial electrical resistance (TEER) of brain endothelial monolayers, indicating the tightness of TJs reached 300 ohm&#183;cm2 on average. The endothelial permeability coefficients (Pe) for lucifer yellow (LY) was highly reproducible with an average of 0.26 &#177;&#160;0.11 x 10-3 cm/min. Brain endothelial cells organized in monolayers expressed the efflux transporter P-glycoprotein (P-gp), showed a polarized transport of rhodamine 123, a ligand for P-gp, and showed specific transport of transferrin-Cy3 and DiILDL across the endothelial cell monolayer. In conclusion, we provide a protocol for setting up an in vitro BBB model that is highly reproducible due to the quality assurance methods, and that is suitable for research on BBB transporters and receptors.

Setting-up an In Vitro Model of Rat Blood-brain Barrier BBB: A Focus on BBB Impermeability and Receptor-mediated Transport

The aim of the present study was to validate the reproducibility of an in vitro BBB model involving a rat syngeneic co-culture of endothelial cells and astrocytes. The endothelial cell monolayer presented high TEER and low LY permeability. Expression of specific TJ proteins, functional responses to inflammation and functionality of transporters and receptors were assessed.

The blood brain barrier (BBB) specifically regulates molecular and cellular flux between the blood and the nervous tissue. Our aim was to develop and ...

Oxygen-Glucose Deprivation and Reoxygenation as an In Vitro Ischemia-Reperfusion Injury Model for Studying Blood-Brain Barrier Dysfunction

Ischemia-Reperfusion (IR) injury is known to contribute significantly to the morbidity and mortality associated with ischemic strokes. Ischemic cerebrovascular accidents account for 80% of all strokes. A common cause of IR injury is the rapid inflow of fluids following an acute/chronic occlusion of blood, nutrients, oxygen to the tissue triggering the formation of free radicals.
Ischemic stroke is followed by blood-brain barrier (BBB) dysfunction and vasogenic brain edema. Structurally, tight junctions (TJs) between the endothelial cells play an important role in maintaining the integrity of the blood-brain barrier (BBB). IR injury is an early secondary injury leading to a non-specific, inflammatory response. Oxidative and metabolic stress following inflammation triggers secondary brain damage including BBB permeability and disruption of tight junction (TJ) integrity.
Our protocol presents an in vitro example of oxygen-glucose deprivation and reoxygenation (OGD-R) on rat brain endothelial cell TJ integrity and stress fiber formation. Currently, several experimental in vivo models are used to study the effects of IR injury; however they have several limitations, such as the technical challenges in performing surgeries, gene dependent molecular influences and difficulty in studying mechanistic relationships. However, in vitro models may aid in overcoming many of those limitations. The presented protocol can be used to study the various molecular mechanisms and mechanistic relationships to provide potential therapeutic strategies. However, the results of in vitro studies may differ from standard in vivo studies and should be interpreted with caution.

Oxygen-Glucose Deprivation and Reoxygenation as an In Vitro Ischemia-Reperfusion Injury Model for Studying Blood-Brain Barrier Dysfunction

Ischemia-Reperfusion (IR) injury is associated with a high rate of morbidity and mortality. The goal of the in vitro model of oxygen-glucose deprivation and reoxygenation (OGD-R) described here is to assess the effects of ischemia reperfusion injury on a variety of cells, particularly in blood-brain barrier (BBB) endothelial cells.

Ischemia-Reperfusion (IR) injury is known to contribute significantly to the morbidity and mortality associated with ischemic strokes. Ischemic ...

A Rat Carotid Balloon Injury Model to Test Anti-vascular Remodeling Therapeutics

The rat carotid balloon injury is a well-established surgical model that has been used to study arterial remodeling and vascular cell proliferation. It is also a valuable model system to test, and to evaluate therapeutics and drugs that negate maladaptive remodeling in the vessel. The injury, or barotrauma, in the vessel lumen caused by an inflated balloon via an inserted catheter induces subsequent neointimal growth, often leading to hyperplasia or thickening of the vessel wall that narrows, or obstructs the lumen. The method described here is sufficiently sensitive, and the results can be obtained in relatively short time (2 weeks after the surgery). The efficacy of the drug or therapeutic against the induced-remodeling can be evaluated either by the post-mortem pathological and histomorphological analysis, or by ultrasound sonography in live animals. In addition, this model system has also been used to determine the therapeutic window or the time course of the administered drug. These studies can leadto the development of a better administrative strategy and a better therapeutic outcome. The procedure described here provides a tool for translational studies that bring drug and therapeutic candidates from bench research to clinical applications.

The rat carotid balloon injury model described below allows researchers to evaluate drugs or therapeutics that negate injury-induced arterial hyperplasia. Detailed pre-surgical preparation, surgical procedure, and post-surgical cares of the animal are described.

The rat carotid balloon injury is a well-established surgical model that has been used to study arterial remodeling and vascular cell proliferation. It is ...

Retroductal Submandibular Gland Instillation and Localized Fractionated Irradiation in a Rat Model of Salivary Hypofunction

Normal tissues that lie within the portals of radiation are inadvertently damaged. Salivary glands are often injured during head and neck radiotherapy. Irreparable cell damage results in a chronic loss of salivary function that impairs basic oral activities, and increases the risk of oral infections and dental caries. Salivary hypofunction and its complications gravely impact a patient's comfort. Current symptomatic management of the condition is ineffective, and newer therapies to assuage the condition are needed. 
Salivary glands are exocrine glands, which expel their secretions into the mouth via excretory ducts. Cannulation of these ducts provides direct access to the glands. Retroductal delivery of a contrast agent to major salivary glands is a routine out-patient procedure for diagnostic imaging. Using a similar procedure, localized treatment of the glands is feasible. However, performing this technique in preclinical studies with small animals poses unique challenges. In this study we describe the technique of retroductal administration in rat submandibular glands, a procedure that was refined in Dr. Bruce Baum's laboratory (NIH)1, and lay out a procedure for local gland irradiation.

Salivary gland hypofunction, a major adverse effect of head and neck radiotherapy diminishes a patient's quality of life. The demonstration of efficacy of new therapies in animal models is a prerequisite before clinical transition. This protocol describes retroductal administration and local irradiation of rat submandibular glands.

Normal tissues that lie within the portals of radiation are inadvertently damaged. Salivary glands are often injured during head and neck radiotherapy. ...

In Vitro Assays to Assess Blood-brain Barrier Mesh-like Vessel Formation and Disruption

Blood-brain barrier (BBB) coverage plays a central role in the homeostasis of the central nervous system (CNS). The BBB is dynamically maintained by astrocytes, pericytes and brain endothelial cells (BECs). Here, we detail methods to assess BBB coverage using single cultures of immortalized human BECs, single cultures of primary mouse BECs, and a humanized triple culture model (BECs, astrocytes and pericytes) of the BBB. To highlight the applicability of the assays to disease states, we describe the effect of oligomeric amyloid-&#946; (oA&#946;), which is an important contributor to Alzheimer&#39;s disease (AD) progression, on BBB coverage. Further, we utilize the epidermal growth factor (EGF) to illuminate the drug screening potential of the techniques. Our results show that single and triple cultured BECs form meshwork-like structures under basal conditions, and that oA&#946; disrupts this cell meshwork formation and degenerates the preformed mesh structures, but EGF blocks this disruption. Thus, the techniques described are important for dissecting fundamental and disease-relevant processes that modulate BBB coverage.

In Vitro Assays to Assess Blood-brain Barrier Mesh-like Vessel Formation and Disruption

Maintaining blood-brain barrier coverage is key for the homeostasis of the central nervous system. This protocol describes in vitro techniques to delineate the fundamental and pathological processes that modulate blood-brain barrier coverage.

Blood-brain barrier (BBB) coverage plays a central role in the homeostasis of the central nervous system (CNS). The BBB is dynamically maintained by ...

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

The aim of this protocol presents an optimized procedure for the purification and cultivation of pBECs and to establish in vitro blood-brain barrier (BBB) models based on pBECs in mono-culture (MC), MC with astrocyte-conditioned medium (ACM), and non-contact co-culture (NCC) with astrocytes of porcine or rat origin. pBECs were isolated and cultured from fragments of capillaries from the brain cortices of domestic pigs 5-6 months old. These fragments were purified by careful removal of meninges, isolation and homogenization of grey matter, filtration, enzymatic digestion, and centrifugation. To further eliminate contaminating cells, the capillary fragments were cultured with puromycin-containing medium. When 60-95% confluent, pBECs growing from the capillary fragments were passaged to permeable membrane filter inserts and established in the models. To increase barrier tightness and BBB characteristic phenotype of pBECs, the cells were treated with the following differentiation factors: membrane permeant 8-CPT-cAMP (here abbreviated cAMP), hydrocortisone, and a phosphodiesterase inhibitor, RO-20-1724 (RO). The procedure was carried out over a period of 9-11 days, and when establishing the NCC model, the astrocytes were cultured 2-8 weeks in advance. Adherence to the described procedures in the protocol has allowed the establishment of endothelial layers with highly restricted paracellular permeability, with the NCC model showing an average transendothelial electrical resistance (TEER) of 1249 &#177; 80 &#937; cm2, and paracellular permeability (Papp) for Lucifer Yellow of 0.90 10-6 &#177; 0.13 10-6 cm sec-1 (mean &#177; SEM, n=55). Further evaluation of this pBEC phenotype showed good expression of the tight junctional proteins claudin 5, ZO-1, occludin and adherens junction protein p120 catenin. The model presented can be used for a range of studies of the BBB in health and disease and, with the highly restrictive paracellular permeability, this model is suitable for studies of transport and intracellular trafficking.

Improved Method for the Establishment of an In Vitro Blood-Brain Barrier Model Based on Porcine Brain Endothelial Cells

The aim of the protocol is to present an optimized procedure for the establishment of an in vitro blood-brain barrier (BBB) model based on primary porcine brain endothelial cells (pBECs). The model shows high reproducibility, high tightness, and is suitable for studies of transport and intracellular trafficking in drug discovery.

The aim of this protocol presents an optimized procedure for the purification and cultivation of pBECs and to establish in vitro blood-brain barrier (BBB) ...

Isometric Contractility Measurement of the Mouse Mesenteric Artery Using Wire Myography

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and drugs. It is widely used in many studies on the physiological functions of vascular smooth muscle, the pathogenesis of vascular diseases such as hypertension, and the development of smooth muscle relaxant drugs. The mouse is a widely used model animal with a large pool of disease models and genetically modified strains. We introduced this method to measure the isometric contraction of mouse mesenteric artery in detail. A 1.4-mm segment of mouse mesenteric resistance artery was isolated and mounted on a myograph chamber by passing two steel wires through its lumen. After equilibration and normalization steps, the vessel segment was potentiated by a high-K+ solution twice prior to the contraction assay. As an example of the application of this method in drug development, we measured the relaxant effect of a novel natural substance, neoliensinine, isolated from a Chinese herb, embryos of the lotus seed (Nelumbo nucifera Gaertn.) on mouse mesenteric arteries. The vessel segments mounted on the myograph chamber were stimulated with a high-K+ solution. When the force tension reached a stable sustained phase, cumulative doses of neoliensinine were added to the chamber. We found that neoliensinine had a dose-dependent relaxant effect on smooth muscle contraction, thus suggesting that it bears potential activity against hypertension. In addition, as the vessel segment can survive at least 4 hours after mounting and maintain contractility induced by the high-K+ solution for many times, we suggest that the wire myograph system may be used for the time-consuming process of drug screening.

The wire myograph technique is used to investigate vascular smooth muscle functions and screen new drugs. We report a detailed protocol for measuring the isometric contractility of the mouse mesenteric artery and for screening new relaxants of vascular smooth muscle.

The wire myograph technique is used to assess the contractility of vascular smooth muscles in response to depolarization, GPCR agonists/inhibitors and ...