Cholecystokinin Influences in the Medial Preoptic Area on Lordosis Behavior of Male and Female Rats
Priest, Catherine Ann
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The distribution of the neuroactive peptide cholecystokinin (CCK-8) in the rat hypothalamus and limbic system has been shown to overlap with that of estrogen containing cells in a number of areas which are relevant to the modulation of reproductive behavior. Additionally, exogenous CCK-8 has been shown both to facilitate and to inhibit lordosis in the female after peripheral and central injection, and to facilitate lordosis in the castrated male after central injection; site-specific injections of CCK-8 into the female ventromedial hypothalamus have also been shown to inhibit lordotic display. The present study was designed to examine further the behavioral effects of CCK-8 after injections into the medial preoptic area (MPOA) of estrogen-primed, castrated male and female rats. Lordotic behavior was significantly increased by MPOA injections of CCK-8 in castrated males that were given estradiol benzoate injections on the three days before behavioral testing, but the effect was not seen in unprimed, castrated males. A similar trend toward facilitation was suggested after injection of CCK-8 in estrogen-primed females. The current results strongly support the hypothesis that a CCK-receptive, estrogen sensitive circuit modulates lordosis in both male and female rats.