Hormonal integration of neurochemical and sensory signals governing female reproductive behavior

This review focuses on findings from our laboratory regarding mechanisms by which the ovarian steroid hormones, estradiol (E-2) and progesterone (P), act in the hypothalamus (HYP) to regulate the expression of lordosis, an important component of female reproductive behavior in rats and many other species. The first section summarizes recent work suggesting that cGMP, perhaps via P-receptor activation, may be an intracellular mediator of the facilitatory actions of a variety of hormones and neurotransmitters on lordosis behavior in E-2-primed rats. In the second section, we focus on E-2 and P regulation of norepinephrine (NE) neurotransmission in the HYP. We review evidence that ovarian hormones act both peripherally and centrally to determine whether NE is released in the HYP in response to copulatory stimuli. We also suggest that the steroid milieu determines the cellular responses of hypothalamic neurons to released NE, favoring the activation of pathways implicated in the facilitation of both lordosis behavior and the preovulatory gonadotropin surge. It is likely that E-2 and P have similar actions on other neurotransmitter and neuromodulator systems, thereby maximizing the probability that females are sexually receptive during the periovulatory period. (C) 1999 Elsevier Science B.V. All rights reserved.