Effects of para-chlorophenylalanine (a serotonin depletor) on conditioned alternation in a choice chamber

The effects of the serotonin depleting drug para-chlorophenyl- alanine (P-CPA) on conditioned alternation in the U-maze were examined. Rats given P-CPA and nondrugged rats received reward contingent upon alternation. Every S received reward on the first trial of each day whether S chose the left or right maze arm. On trials two and three, contingent reward Ss had to choose the arm opposite that chosen on the previous trial to obtain reward. To evaluate the effectiveness of the reward contingency, the 'spontaneous' alternation level was determined by observing the alternation behavior of a group of nondrugged Ss yoked to some of the contingent reward nondrugged control Ss. A yoked rat received reward only if its contingent reward counterpart alternated and received reward. Training was given for 30 days with a 30 min. ITI. Because there was no effect of the reward contingency on alternation scores after 30 days of training with a 30 min. ITI, the ITI was reduced to 30 sec. for an additional 20 days of training. The reward contingent Ss did perform at higher alternation levels than the yoked rats when the ITI was reduced to 30 sec. There was no difference in alternation performance between the drugged and nondrugged contingent reward groups' during the experiment. The failure to find a P-CPA effect on conditioned alternation during the short ITI phase of the experiment implies that serotonin does not have an important role in memory processes. When the rate of development of rapid running in the maze was examined by comparing the first trial latencies of drugged and control Ss, the drugged Ss evidenced faster acquisition than the nondrugged Ss but asymptotic running times were unaffected by P-CPA. P-CPA was shown to reduce food intake and body weight.