Neuroanatomical distribution of oxytocin receptor binding in the female rabbit forebrain: Variations across the reproductive cycle.

Oxytocin receptors (OTR) have been characterized in the brains of several mammals, including rodents, carnivores, and primates. Their species-specific distribution in the brain has been associated with species differences in social organization, including mating strategy and parenting behavior. In several species, the density of OTR binding in specific brain regions varies according to reproductive condition, including ovarian cycle, pregnancy and lactation. Rabbits are induced ovulators, polygamous, and monoparental but their distribution and regulation of brain OTR has not been described. Here we used receptor autoradiography to quantitatively characterize OTR binding in the brains of estrous, ovariectomized, late pregnant, and lactating does. Intense binding occurred in the prefrontal cortex (PFC), preoptic area (POA), lateral septum (LS; dorsal and ventral), hippocampus, and medial amygdala. Variations among the experimental groups were seen only in PFC, POA, LS. Ovariectomy increased OTR density in PFC but had the opposite effect in POA. Lactating does had significantly reduced OTR density, relative to late pregnancy, in PFC and POA. Our results are consistent with a possible role of OT in modulating social and maternal behavior in rabbits since the brain regions sensitive to OT have been implicated in social interaction, learning and memory, olfactory processing and maternal behavior.