Effect of cyproheptadine treatment on conditioned avoidance response in female rats

1. The percentage of conditioned avoidance response was higher during proestrus compared to diestrus. 2. Cyproheptadine (CPH) significantly enhanced avoidance behavior during diestrus. 3. On the other hand, CPH treatment did not alter avoidance behavior during proestrus. 4. Serum progesterone and testosterone levels were determined at the end of 60 trials for acquisition of conditioned avoidance response after prolonged (12-15 days) CPH treatment (0.5 mg/kg for 24 h per os (p.o.). 5. Prolonged CPH treatment lowered adrenal testosterone levels, and rats with impaired avoidance had higher testosterone and progesterone levels. 6. The results of this study indicate a positive role for CPH in the acquisition of avoidance response during diestrus, and a negative effect of progesterone and adrenal testosterone on the avoidance response.