The nucleus accumbens dopamine increase, typically triggered by sexual stimuli in male rats, is no longer produced when animals are sexually inhibited due to sexual satiety

Abstract

Rationale: Exposure of male rats to an inaccessible receptive female and copulation increases dopamine (DA) levels in the nucleus accumbens (NAcc). Males copulating to satiety become sexually inhibited and most of them do not display sexual activity when presented with a sexually receptive female 24 h later. This inhibitory state can be pharmacologically reversed. There are no studies exploring NAcc DA levels during this sexual inhibitory state.

Objectives: To characterize changes in NAcc DA and its metabolites' levels during sexual satiety development, during the well-established sexual inhibitory state 24 h later, and during its pharmacological reversal.

Methods: Changes in NAcc DA and its metabolites were measured in sexually experienced male rats, using in vivo microdialysis, during copulation to satiety, when presented to a new sexually receptive female 24 h later, and during the pharmacological reversal of the sexual inhibition by anandamide.

Results: NAcc DA levels remained increased during copulation to satiety. DA basal levels were significantly reduced 24 h after copulation to satiety, as compared to the initial basal levels. Presenting a receptive female behind a barrier 24 h after satiety did not induce the typical NAcc DA elevation in the sexually satiated males but there was a decrease that persisted when they got access to the female, with which they did not copulate. Anandamide injection slightly increased NAcc DA levels coinciding with sexual satiety reversal.

Conclusions: Reduced NAcc DA concentrations coincide with the inhibition of an instinctive, natural rewarding behavior suggesting that there might be a DA concentration threshold needed to be responsive to a rewarding stimulus.

Keywords: Anandamide; Dopamine extracellular concentrations; Male sexual behavior; Mesolimbic system; Microdialysis; Natural reward; Nucleus accumbens; Sexual inhibition; Sexual motivation; Sexual satiety.