Infusions of bicuculline to the ventral tegmental area attenuates sexual, exploratory, and anti-anxiety behavior of proestrous rats

Abstract

Actions of 5α-pregnan-3α-ol-20-one (3α,5α-THP), in the midbrain ventral tegmental area (VTA) modulate sexual receptivity of female rats. Actions of 3α,5α-THP at GABAergic substrates in the VTA are known to modulate consummatory aspects of sexual behavior among rodents, such as lordosis. However, the extent to which GABA A receptors in the VTA are important for appetitive (exploratory, anti-anxiety, social) aspects of sexual receptivity is not well-understood. Proestrous rats were bilaterally-infused with saline or bicuculline (100 ng), a GABA A receptor antagonist, to the VTA or missed control sites. Rats were assessed for exploratory/anti-anxiety (open field/elevated plus maze), social (social interaction), and sexual (paced-mating) behavior. Compared to saline or missed site controls, intra-VTA bicuculline significantly reduced the number of central entries in an open field, time spent on the open arms of an elevated plus maze, frequency and intensity of lordosis, anti-aggression towards a male, pacing of sexual contacts, and 3α,5α-THP concentrations in midbrain and hippocampus. Bicuculline-infused rats also displayed less affiliation with a novel conspecific, fewer sexual solicitations, and had lower 3α,5α-THP concentrations in diencephalon and cortex, albeit these were not significant differences. Thus, actions at GABA A receptors in the midbrain VTA are essential for appetitive and consummatory aspects of sexual receptivity among rats.