Bayless, Davis, Yang et al. have mapped the circuit for mating behavior in male mice. They show that neurons that express substance P (also known as tachykinin 1) in the principal nucleus of the bed nucleus of the stria terminalis (BNSTprTac1 neurons) are sufficient to signal the presence of a female mouse. These cells synapse onto tachykinin receptor 1-expressing neurons in the preoptic area (POATacr1 neurons), and activation of this projection was necessary and sufficient to induce mating, but not aggression. Activation of POATacr1 neurons induced mating and even mounting of a toy mouse. Substance P was released by BNSTprTac1 neurons when a male mouse encountered a female, causing excitatory long-term potentiation in POATacr1 neurons; this might serve as a molecular timer for initiation of mating. Optogenetic activation of POATacr1 neurons immediately after ejaculation triggered mating behavior, eliminating the refractory period, which normally lasts around 5 days. Activation of these neurons was rewarding to the mice. The authors also showed that pheromone information is conveyed directly to BNSTprTac1 neurons from the accessory olfactory bulb, and that POATacr1 neurons project to the periaqueductal grey and ventral tegmental area, which give rise to motor and reward outputs, respectively. These data may be useful in developing treatments for human sexual dysfunction.
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