OXYTOCIN AND COMPLEX SOCIAL-BEHAVIOR - SPECIES COMPARISONS

The neurohypophyseal peptide hormone oxytocin functions as a neuropept ide in several brain areas in addition to its role as a posterior pitu itary 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 sp ecies is remarkably different reproductive behavior strategies. The pr airie vole forms long-term monogamous relationships; the montane vole is polygamous. One potential measure of the formation of a pair bond i n prairie voles is the development of intense aggressive behavior dire cted 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 adminis tered after mating. Oxytocin had relatively modest effects on the beha vior of montane voles, and neither the behavior nor the peptide effect s were affected by mating experience. The data indicate that differenc es in peptide binding in these two species of vole may be functionally related to differences in social behavior.