Cholecystokinin-octapeptide produces inhibition of lordosis in the female rat.

The peripheral administration of 3 micrograms/kg CCK-8 produced inhibition of lordosis behavior in ovariectomized female rats primed with estradiol benzoate (EB) and progesterone (P). In Experiment 2, an interaction between CCK-8 and P was evident, with the inhibitory effects of CCK-8 being observed with P doses of 100 and 150 micrograms, but not 250 micrograms. No interaction between CCK-8 and EB was evident, as CCK-8 had no effect on lordosis behavior induced by chronic administration of EB alone. The ineffectiveness of CCK-8 in animals treated with high doses of P, or EB administered chronically, suggests that CCK-8 does not inhibit lordosis via a toxic or non-specific mechanism.