Sex Behavior

Abstract

Sexual, as opposed to asexual, reproduction increases variability and provides a mechanism for repair of DNA and possibly reduction of pathogen specialization. Sex differentiation can be can be controlled by either environmental factors (as in some fish, amphibians, and reptiles) or by genes (as in other fish, amphibians, and reptiles, and all birds and mammals). Genetic influences on sex differentiation are typically mediated by hormones during early development; however, the specific hormones and their modes of action vary among species. Most hormonal actions require binding to intracellular receptors that act as regulators of gene transcription; however, hormones may also act rapidly via membrane receptors. Activational effects of hormones in adulthood act on the neural substrates that were differentiated during development. There is some conservation throughout evolution in the brain areas that control masculine and feminine sexual behaviors. The medial preoptic area, at the anterior end of the hypothalamus, is a major control hub for masculine behavior in all vertebrate species. Similarly, the ventromedial hypothalamus is important for feminine receptive behaviors of numerous species. Sexually relevant stimuli and motor outputs are processed by neurons that may require hormones to increase their responsiveness. The same brain areas and hormones that control sexual behavior also control other social behaviors.

Preoptic Glutamate Facilitates Male Sexual Behavior

“…It receives indirect input from every sensory modality (Simerly and Swanson, 1986) and sends projections to structures critical for the initiation and patterning of copulation (COP) (Simerly and Swanson, 1988). Lesions of the MPOA inhibited male sexual behavior in all studied species; conversely, stimulation facilitated several copulatory measures (for review, see Hull et al, 2002;Hull and Dominguez, 2003). Stimulation of the rats' MPOA also elicited erectile responses (Giuliano et al, 1997) and the urethrogenital reflex, a proposed model for orgasm (Marson and McKenna, 1994).…”