Neural and Hormonal Control of Sexual Behavior

Abstract

Gonadal hormones contribute to the sexual differentiation of brain and behavior throughout the lifespan, from initial neural patterning to "activation" of adult circuits. Sexual behavior is an ideal system in which to investigate the mechanisms underlying hormonal activation of neural circuits. Sexual behavior is a hormonally regulated, innate social behavior found across species. Although both sexes seek out and engage in sexual behavior, the specific actions involved in mating are sexually dimorphic. Thus, the neural circuits mediating sexual motivation and behavior in males and females are overlapping yet distinct. Furthermore, sexual behavior is strongly dependent on circulating gonadal hormones in both sexes. There has been significant recent progress on elucidating how gonadal hormones modulate physiological properties within sexual behavior circuits with consequences for behavior. Therefore, in this mini-review we review the neural circuits of male and female sexual motivation and behavior, from initial sensory detection of pheromones to the extended amygdala and on to medial hypothalamic nuclei and reward systems. We also discuss how gonadal hormones impact the physiology and functioning of each node within these circuits. By better understanding the myriad of ways in which gonadal hormones impact sexual behavior circuits, we can gain a richer and more complete appreciation for the neural substrates of complex behavior.

Keywords: activation; gonadal hormones; reproductive behavior; sex differences; sex hormones.

Figure 1.

Neural circuits of male and female sexual behavior. Regions are color-coded based on major contributions to either appetitive or consummatory aspects of sexual behavior.

Figure 2.

Hormonal control of female sexual behavior. The sequential rise in estrogen followed by progesterone across the estrous cycle (top) causes female rodents to be sexually receptive near ovulation (middle). This is mediated by an array of neurophysiological changes to the brain induced by hormonal signaling (bottom). Gonadal steroid hormones signal both through nuclear receptors and membrane-bound receptors (bottom right). This signaling regulates gene expression, structural remodeling, neuronal activity, and changes in synaptic properties in a region-specific manner.