Microinjection of cholecystokinin into the medial preoptic nucleus facilitates lordosis behavior in the female rat.

We examined the effect of cholecystokinin (CCK) on lordosis behavior when administered into the medial preoptic area or the nucleus accumbens (NAcc) of ovariectomized estrogen-primed female rats. The frequency of lordotic responses was measured subsequent to unilateral microinjections of sulphated octapeptide CCK (sCCK-8) into the medial preoptic nucleus (MPN) or the NAcc. In the first experiment, three doses of sCCK-8 (1, 5, and 50 ng) microinjected into the MPN, and 50 ng injected into the NAcc produced a marked facilitation of lordosis. In a separate experiment, unilateral injections of an undiluted sCCK-8 antiserum into the MPN produced significant reduction in lordosis behavior in highly receptive females when compared with a normal rabbit serum injected control group. The results of the present study indicate that the CCK innervation of the MPN is involved in the neural regulation of lordosis behavior in the female rat.