A neural circuit for male sexual behavior and reward.

Male sexual behavior is innate and rewarding. Despite its centrality to reproduction, a molecularly specified neural circuit governing innate male sexual behavior and reward remains to be characterized. We have discovered a developmentally wired neural circuit necessary and sufficient for male mating. This circuit connects chemosensory input to BNSTprTac1 neurons, which innervate POATacr1 neurons that project to centers regulating motor output and reward. Epistasis studies demonstrate that BNSTprTac1 neurons are upstream of POATacr1 neurons, and BNSTprTac1-released substance P following mate recognition potentiates activation of POATacr1 neurons through Tacr1 to initiate mating. Experimental activation of POATacr1 neurons triggers mating, even in sexually satiated males, and it is rewarding, eliciting dopamine release and self-stimulation of these cells. Together, we have uncovered a neural circuit that governs the key aspects of innate male sexual behavior: motor displays, drive, and reward.

Investigation of Activated Mouse Olfactory Sensory Neurons via Combined Immunostaining and in situ Hybridization.

Animals rely on chemical communication to convey and perceive relevant environmental information, ranging from assessment of food quality to detection of available mating partners or threats. In mice, this task is executed primarily by the olfactory system and its underlying subsystems, including the main and accessory olfactory systems. Both have peripheral organs populated by sensory neurons expressing G-protein coupled receptors able to bind chemical cues that reach the nasal cavity. Even though the molecular characteristics of these receptors is well understood, little is known about their cognate specific ligands. The method described here combines in situ hybridization detection of olfactory or vomeronasal receptors with immunodetection of phosphorylated ribosomal protein S6 (pS6) - a marker of neuronal activation. This protocol was devised to identify neurons activated after a single event of exposure to purified or complex chemical stimuli detected by the olfactory organs. Importantly, this technique allows the investigation of neurons triggered in biologically relevant contexts. Ideally, this method should be used to probe the molecular biology of the olfactory system and to study olfactory behaviors.