SEXUAL-ACTIVITY INCREASES DOPAMINE TRANSMISSION IN THE NUCLEUS-ACCUMBENS AND STRIATUM OF FEMALE RATS

In vivo microdialysis was used to monitor extracellular concentrations of dopamine (DA), and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the nucleus accumbens and dorsal striatum of sexually active female rats during tests of locomotor activity, exposure to a novel chamber, exposure to sex odors, the presentation of a sexually active male rat, and copulation. DA increased slightly but significantly in the nucleus accumbens when a sexually active male was placed behind a wire-mesh screen, and further during copulation. DA also increased significantly in the dorsal striatum during copulation; however, the magnitude of this effect was significantly lower than that observed in the nucleus accumbens. The metabolites DOPAC and HVA generally followed DA with a delay, and increased significantly during copulation in both regions. In contrast, forced locomotion on a rotating drum, exposure to a novel testing chamber, and exposure to sex odors did not increase DA significantly in either region, although forced locomotion increased DOPAC significantly in both regions, and HVA significantly in the nucleus accumbens. The magnitude of DA release in the nucleus accumbens was significantly greater during copulation than running, whereas no significant difference was detected for striatal DA release between these two behavioral conditions. These results indicate that novelty or locomotor activity alone do not account for the increase in DA observed in the nucleus accumbens of female rats during copulation, and suggest that DA transmission in the nucleus accumbens is associated with anticipatory and consummatory aspects of sexual activity, as it is in male rats. In the dorsal striatum, however, DA release during copulation may reflect an increase in locomotor activity associated with active pacing of the male.