This video demonstrates a new approach in studying drug abuse by combining traditional conditioned place preference and self-administration procedures. First, baseline preferences for two distinct operant environments is determined. Self-administration sessions then begin in which rats self-administer cocaine in only one of the distinctive operant environments.
Following conditioning, the amount of time the animals choose to spend in either of the operant environments is measured, changes in place, preference and rates of drug self-administration can then be measured and correlated. Hi, I'm Allison Fiducia from the laboratory of Dr.Christine Elle in the College of Pharmacy, the division of pharmacology and toxicology at the University of Texas at Austin. And I'm Christine Elle.
Today we would like to show you a novel apparatus that can be used in several different ways to study drug reinforcement and addiction in rats. We use this procedure in our laboratory to study the condition effects of cocaine self-administration. So let's get started.
To begin preparations for drug reinforcement experiments, first train male rats to press a lever for a food reward. Next construct intravenous catheters, which will be used for drug self-administration. Catheters are made out of stainless steel cannula and Celeste tubing and should be flushed with methanol and water.
Then air dried during their preparation on the day of surgery, bathe them in 70%ethanol. When the catheters are completed, rats undergo a jugular catheterization surgical procedure to allow for drug self-administration. During experiments, anesthetize a rat with two and a half to 4%isof fluorine.
Next, shave the head and chest, disinfect the areas with Betadine solution. Then place it on a sterile pad following surgery. Monitor the rat for several hours before returning it to the animal colony.
Maintain catheter patency by daily flushing with 0.1 milliliters of a 0.9%saline, heparin and menton solution to prepare the cocaine used in the experiments, dissolve it in an isotonic saline solution in the appropriate dose concentrations according to animal weights with the animals and drug delivery prepared. Let's take a look at the apparatus that is used during experiments. The apparatus used during experiments is constructed out of two single lever chambers, equipped with house and stimulus lights, and three sets of photo beams, which are used to measure locomotor activity.
Chambers are joined together by a constructed plexiglass alley. The alley consists of two black walls with white stripes and two metal walls, a clear plexiglass top and a white plexiglass floor. The two operant chambers have steel grid rod floors installed removable metal cage bottoms.
Visual and olfactory cues are placed within the operant chamber to create unique distinguishable environments. In one of the environments, the threat will have access to cocaine injections. In the alternate environment, the threat will have access only to saline injections.
The visual cues consist of either white or black felt material attached to the front and back walls and over the cage top. The olfactory cues are oil-based sense of rows or cinnamon saturating a cotton ball located under the rod floor of the chamber. During experiments, Libra responses and locomotor activity data are recorded with a Med Pentium 100 megahertz computer equipped with med PC software.
Now that we've seen the experimental apparatus, let's see how to collect data. The experimental procedure occurs over multiple days, starting with baseline preference tests lasting two days, followed by drug self-administration sessions lasting eight or 16 days and ending with a conditioned place preference test. To begin collecting baseline preference measurements, place the rat in the center alley with access to both operant chambers for 20 minutes.
Immediately after placing the rat in the chamber simultaneously activate the video camera med PC software program and timer. After 20 minutes, remove the rat from the chamber and place it back into the home cage. The day after the last baseline test, begin drug self-administration sessions.
First, place the sensory cues and then place a panel to block off access from the plexiglass center alley into the chamber. Now attach the animal's catheter inlet to the mounted drug syringe to start the session. First, place the animal into the chamber.
After closing the operant chamber door, start the med PC program and timer so that cocaine accesses available for one hour. Cocaine is administered using a progressive ratio schedule of reinforcement. This schedule requires progressively more lever responses to receive each successive cocaine injection.
Each injection consists of a dose of 0.75 milligrams per kilogram on alternating days. In the alternate environment, the progressive ratio schedule is also used for saline injections. At the end of each self-administration session, disconnect the wrap from the drug tubing, remove it from the chamber, and place it back in the home cage.
The day after the last self-administration session, conduct the conditioned place preference test. The procedure for this test is the same as the baseline measurements. Now let's see how to assess and analyze the data.
During data assessment and experimenter blind group assignments determines the amount of time the animal spent in each compartment. The experimenter reviews the videotape to count entrances and exits between the compartments for 15 minute period, beginning five minutes after placement within the apparatus. The same procedures used to determine baseline preference and CPP test scores.
Differences between baseline measurements and post conditioning CPP scores are used to determine drug conditioning effects. Post conditioning difference scores are calculated by subtracting the amount of time spent in the salient paired compartment from the amount of time spent in the drug paired compartment during the CPP test. The baseline difference scores are similarly calculated and subtracted from the CPP difference scores.
Statistical analysis on different score changes from baseline to test sessions can be performed to determine effects of drug conditioning. Shown here is a representative graph of baseline and CPP test scores. CPP test scores were significantly greater than baseline scores indicating a preference for the cocaine environment.
After conditioning correlation analysis for total drug leave responses and CPP difference test scores are illustrated here. The cocaine long-term group was the only group to show a significant positive correlation between drug leave responses and CPP test scores. We have just shown you how to combine traditional condition, place preference, and self-administration methods for a novel approach to studying drug reinforcement in rats.
When doing this procedure, it's important to maintain good record keeping. So that's it. Thanks for watching and good luck with your experiments.
