No abstract

Pleasurable touch during social behavior is the key to building familial bonds and meaningful connections. One form of social touch occurs during sex. Although sexual behavior is initiated in part by touch, and touch is ongoing throughout copulation, the identity and role of sensory neurons that transduce sexual touch remain completely unknown. A population of sensory neurons labeled by the G-protein coupled receptor Mrgprb4 detect stroking touch in mice. Here, we study the social relevance of this population by genetically engineering mice to allow activation or ablation of Mrgprb4-lineage neurons and reveal that these neurons are required for sexual receptivity and sufficient to activate reward circuitry. Even in social isolation, optogenetic stimulation of Mrgprb4-lineage neurons through the back skin is sufficient to induce a conditioned place preference and a striking lordosis-like copulatory posture in females. In the absence of Mrgprb4-lineage neurons, female mice no longer find male mounts rewarding: sexual receptivity is supplanted by aggression and a coincident decline in dopaminergic release in the mesolimbic reward pathway. In addition to sexual behavior, Mrgprb4-lineage neurons are also required for social postures induced by female-to-female back touch. Together, these findings reveal a skin-to-brain circuit encoding the rewarding quality of social touch.