Sexual behavior induction of c-Fos in the nucleus accumbens and amphetamine-stimulated locomotor activity are sensitized by previous sexual experience in female Syrian hamsters

Dopamine transmission in the nucleus accumbens can be activated by drugs, s tress, or motivated behaviors, and repeated exposure to these stimuli can s ensitize this dopamine response. The objectives of this study were to deter mine whether female sexual behavior activates nucleus accumbens neurons and whether past sexual experience cross-sensitizes neuronal responses in the nucleus accumbens to amphetamine. Using immunocytochemical labeling, c-Fos expression in different subregions (shell vs core at the rostral, middle, a nd caudal levels) of the nucleus accumbens was examined in female hamsters that had varying amounts of sexual experience. Female hamsters, given eithe r 6 weeks of sexual experience or remaining sexually naive, were tested for sexual behavior by exposure to adult male hamsters. Previous sexual experi ence increased c-Fos labeling in the rostral and caudal levels but not in t he middle levels of the nucleus accumbens. Testing for sexual behavior incr eased labeling in the core, but not the shell, of the nucleus accumbens. To validate that female sexual behavior can sensitize neurons in the mesolimb ic dopamine pathway, the locomotor responses of sexually experienced and se xually naive females to an amphetamine injection were then compared. Amphet amine increased general locomotor activity in all females. However, sexuall y experienced animals responded sooner to amphetamine than did sexually nai ve animals. These data indicate that female sexual behavior can activate ne urons in the nucleus accumbens and that sexual experience can cross-sensiti ze neuronal responses to amphetamine. In addition, these results provide ad ditional evidence for functional differences between the shell and core of the nucleus accumbens and across its anteroposterior axis.