Lesions in Medial Preoptic Area and Bed Nucleus of Stria Terminalis: Differential Effects on Copulatory Behavior and Noncontact Erection in Male Rats

Abstract

The goal of these studies was to assess the regulatory roles of the medial preoptic area (MPOA) and the bed nucleus of the stria terminalis (BST) in sexual arousal, inferred from noncontact erection (NCE) evoked in male rats by remote cues from estrous females. NCE and copulatory behavior were recorded before and after quinolinic acid or radiofrequency (RF) lesions were made in the MPOA (Experiments 1-3) or RF lesions were made in the BST (Experiment 4). All males with MPOA lesions, particularly in the rostral region, displayed severe deficits in copulation but little or no decrement in NCE. In contrast, BST lesions caused relatively moderate deficits in copulation, but they severely impaired NCE. Animals with larger BST lesions, including rostral and caudal medial regions, had more deficits in both copulatory behavior and NCE than did males with smaller lesions confined to the rostral medial BST. These results suggest that (1) the MPOA is critical for copulatory behavior but not for NCE, (2) males that stop copulating after MPOA lesions are still sexually aroused by estrous females, and (3) the BST plays an important role in mediating NCE.

Dopamine, the medial preoptic area, and male sexual behavior

“…Similar patterns of behavior were observed in cats [56] and dogs [57] with MPOA lesions. Furthermore, MPOA lesions did not affect the frequency of masturbation in monkeys [58] or noncontact erections, a measure of psychogenic erections, in rats [59]. In contrast to those studies, lesions of the MPOA diminished preference for a female partner in rats [60 -62] and ferrets [63,64], decreased pursuit of a female by male rats [65], and inhibited precopulatory behavior in marmosets [66], suggesting that the MPOA may indeed be important for the appetitive aspects of sexual behavior.…”

Topography in the preoptic region: Differential regulation of appetitive and consummatory male sexual behaviors

“…The medial SDA in gerbils has long been considered to be homologous to the medial part of the rat MPN, consistent with the fact that cell-body lesions of the rat MPN eliminate mounting behavior [66,74,90]. The SDA pars compacta, a sexually differentiated smaller group of cells located within the medial SDA that is organized by sex steroids during ontogeny, would then be equivalent to the rat SDN-POA [69,156].…”

“…Furthermore, these lesions do not inhibit measures of sexual arousal such as penile erections in response to remote cues from estrous females [90]. In contrast, it was found that lesions to the basolateral amygdala inhibit noncontact erections and the ability of males to acquire learned responses that are rewarded with access to females [67,68,90]. These observations lead to the idea of a double dissociation between brain areas mediating copulatory behavior on the one hand (the mPOA) and appetitive sexual behavior / sexual arousal / sexual motivation on another hand (amygdala, bed nucleus striae terminalis; see [66][67][68]).…”

“…Rats with such lesions still pursue and attempt to mount females [35]; they also perform learned instrumental responses to gain access to females [67,68]. Furthermore, these lesions do not inhibit measures of sexual arousal such as penile erections in response to remote cues from estrous females [90]. In contrast, it was found that lesions to the basolateral amygdala inhibit noncontact erections and the ability of males to acquire learned responses that are rewarded with access to females [67,68,90].…”

Preoptic Glutamate Facilitates Male Sexual Behavior

“…Sexual behavior is severely compromised after removal of the MPOA. Fewer than 30% of rats with MPOA lesions mounted, fewer than 15% intromitted, and fewer than 3% ejaculated, whereas 100% of control animals displayed all three behaviors (Liu et al, 1997). Conversely, stimulation of the MPOA enhances sexual activity.…”