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Abstract
Social encounters often start with routine investigatory behaviors before developing
into distinct outcomes, such as affiliative or aggressive actions. For example, a
female mouse will initially engage in investigatory behavior with a male but will
then show copulation or rejection, depending on her reproductive state. To promote
adaptive social behavior, her brain must combine internal ovarian signals and external
social stimuli, but little is known about how socially evoked neural activity is modulated
across the reproductive cycle [1]. To investigate this, we performed single-unit recordings
in the ventrolateral region of the ventromedial hypothalamus (VMHvl) in freely behaving,
naturally cycling, female mice interacting with conspecifics of both genders. The
VMHvl has been implicated in rodent sociosexual behavior [2, 3]: it has access to
social sensory stimuli [4-8] and is involved in aggression and mating [9-11]. Furthermore,
many VMHvl neurons express ovarian hormone receptors [12, 13], which play a central
role in female sociosexual behavior [14-16]. We found that a large fraction of VMHvl
neurons was activated in the presence of conspecifics with preference to male stimuli
and that the activity of most VMHvl neurons was modulated throughout social interactions
rather than in response to specific social events. Furthermore, neuronal responses
to male, but not female, conspecifics in the VMHvl were enhanced during the sexually
receptive state. Thus, male-evoked VMHvl responses are modulated by the reproductive
state, and VMHvl neural activity could drive gender-specific and reproductive state-dependent
sociosexual behavior.