Organizational and Activational Effects of Dopamine on Male Sexual Behavior
Elaine M. Hull, Daniel S. Lorrain, Jianfang Du, Leslie Matuszewich, Daniel Bitran, J.Ken Nishita, and Laura L. Scaletta
This chapter will summarize evidence that the neurotransmitter dopamine can affect both the developmental organization and the adolescent/adult activation of male rat sexual behavior. Furthermore, these effects are at least partially independent of hormonal influence. Specifically, evidence will be presented that (1) dopaminergic drugs administered perinatally can affect sexual differentiation without altering fetal or adult testosterone levels; (2) dopaminergic drugs, even in the absence of testosterone, can activate maletypical behavior in adult rats; (3) dopamine is released in the medial preoptic area (MPOA) of the basal forebrain of male rats before and during copulation; and (4) MPOA dopamine release in the presence of a receptive female depends on the recent, but not concurrent, presence of testosterone.
It is a central dogma of our field that testosterone and its metabolites masculinize mammalian brains and genitals during early development and activate male-typical behavior in adulthood (e.g., Ellis, 1996b, p. 36). The sex-determining region on the Y chromosome (Sry) of male mammals encodes a transcription factor, testis-determining factor (TDF), which induces the formation of testes from the primordial gonads and stimulates the secretion of testosterone ( Gubbay et al., 1990; Sinclair et al., 1990). In male rats, a surge of testosterone on embryonic Days 18 and 19 ( Weisz & Ward, 1980) is thought to initiate processes of masculinization and defeminization of numerous brain structures, including those that regulate neuroendocrine control and reproductive behavior. Evidence for the central roles of gonadal hormones