Abstract

The neurohypophyseal peptide hormone oxytocin functions as a neuropeptide in several brain areas in addition to its role as a posterior pituitary hormone. Several studies have determined significant differences in patterns of oxytocin receptor binding in the brains of two closely related species of vole. One of the defining features of these two species is remarkably different reproductive behavior strategies. The prairie vole forms long-term monogamous relationships; the montane vole is polygamous. One potential measure of the formation of a pair bond in prairie voles is the development of intense aggressive behavior directed at male conspecifics following a mating bout. Oxytocin had little effect on aggressive behavior when administered before mating but had profound effects on the aggression of male prairie voles when administered after mating. Oxytocin had relatively modest effects on the behavior of montane voles, and neither the behavior nor the peptide effects were affected by mating experience. The data indicate that differences in peptide binding in these two species of vole may be functionally related to difference in social behavior.