Injections of cholecystokinin into the ventromedial hypothalamic nucleus inhibit lordosis behavior in the rat.

In the central nervous system, the ventromedial nucleus of the hypothalamus (VMH) is a primary locus for the induction of lordosis behavior by estrogen. Tissue levels of cholecystokinin and its binding sites in the VMH are modulated by estrogen, suggesting a role for cholecystokinin in the regulation of lordosis behavior. The effects of exogenous cholecystokinin octapeptide (CCK-8) were examined by injecting CCK-8 into the VMH and measuring the frequency of lordotic responses. CCK-8 inhibited the frequency of lordotic responses in a dose-related fashion when the control rats had lordosis quotients of 60 and above. This inhibition is in agreement with previously reported results after peripheral injection of CCK-8, and is consistent with the hypothesis that CCK-8 in the VMH in involved in the regulation of lordosis behavior in the estrogen-primed rat.