Estrogen and endogenous opioids regulate CCK in reproductive circuits

This review focuses on the interaction of estrogen with the cholecystokinin (CCK) and endogenous opioid peptide systems in the medial preoptic nucleus , and how these interactions result in alterations of a stereotypic female reproductive behavior-lordosis. The medial preoptic nucleus is an integral part of a circuit controlling lordosis that extends from the limbic system through the hypothalamus. Estrogen alters the integration of sensory inform ation in the circuit that results in the display of sexually receptive beha vior. Estrogen determines the activity of CCK and endogenous opioid peptide systems through regulation of expression, release and interaction with spe cific receptors. Studies of each system individually have indicated that th ey are pivotal to the expression of lordosis. Recent studies demonstrate an estrogen-dependent interaction between endogenous opioid and CCK systems t hat control reproductive behavior. (C) 2001 Elsevier Science Inc. All right s reserved.