Individually-determined differences in the effects of psychotropic drugs on memory (experiments on rats)

Using the methods for "staircase-maze" training with positive (alimentary) reinforcement and "steps down" passive avoidance with punishment (electroshock) reinforcement, we divided the experimental animals into three groups: "good", "intermediate", and "poor" learners. In the course of seven days the animals of the three groups were treated with five substances and were then tested for retention with both methods. Amphetamine at single doses of 0.1 and 0.5 mg/kg was injected s. c. 30 min before the retention test given on the 7th day after the end of training. The other four drugs were administered twice daily throughout the period between the end of training and retention testing (seven days). Adafenoxate was applied at a dose of 10 mg/kg, piracetam at doses of 50, 150, and 300 mg/kg, and aniracetam at doses of 50 and 150 mg/kg--all the three drugs were administered orally; citicholine was injected at doses of 10 and 50 mg/kg i. p. The effects of the substances tested significantly differed depending on the animal's belonging to one or another group. Furthermore, depending on the retention test, the drug tested and the dose used, we observed differences in the effects not only in the different groups but also in one and the same group. Not taking into account the individual capabilities of experimental animals to acquire a retention task might lead to an incorrect characterization of such an important property of psychotropic drugs as their effect on memory process.