Decrease of sexual receptivity by prolylendopeptidase inhibitor in female rats.

The effects of a prolylendopeptidase inhibitor, 1-[3-(2-indanylanylacetyl)-L-thioprolyl]pyrrolidine (Z-321), on lordosis behavior were investigated in estrogen and progesterone-treated ovariectomized rats. Females were orally administered 100, 200 or 300 mg/kg Z-321 or the vehicle (control). The mean lordosis quotient in the rats given 300 mg/kg Z-321 was lower than that in control group, but that in rats given 100 or 200 mg/kg Z-321 was not lower. Thus, Z-321 suppressed lordosis in estrogen and progesterone-treated ovariectomized rats. Peptide neurotransmitters, especially those containing proline, are thought to be involved in the inhibitory mechanisms for lordosis behavior.