SPECIES-DIFFERENCES IN VASOPRESSIN RECEPTOR-BINDING ARE EVIDENT EARLYIN DEVELOPMENT - COMPARATIVE ANATOMIC STUDIES IN PRAIRIE AND MONTANE VOLES

Monogamous prairie voles (Microtus ochrogaster) and promiscuous montan e voles (Microtus montanus) exhibit remarkable differences in the dist ribution of vasopressin (AVP) receptors in the adult brain. This diffe rence in receptor distribution is associated with species differences in the behaviors, including pair bond formation and paternal care, fou nd selectively in the monogamous vole. To investigate a potential mech anism for this species difference in AVP receptors, the present study examined the ontogeny of receptor binding in the two species to determ ine whether the adult maps arose from a shared pattern in development. By using I-125-linear-AVP, which is a selective high-affinity ligand for the V-1a receptor, we found early appearance and transient express ion of AVP receptor binding during postnatal development in both speci es. However, the ontogenetic patterns of regional AVP receptor binding were species specific. In the diagonal band, the bed nucleus of the s tria terminalis, and the central nucleus of the amygdala, prairie vole s had higher AVP receptor binding at birth than montane voles, and thi s difference persisted with little variation into adulthood. In these areas, therefore, species differences in AVP receptor binding appeared to be determined primarily by genetic or prenatal factors. In the lat eral septum, both species had low levels of AVP receptor binding at bi rth. Thereafter, the binding increased rapidly in montane voles, but i t remained unchanged in prairie voles. In the cingulate cortex, AVP re ceptor binding in prairie voles showed a peak in early development wit h a subsequent decline and reached the adult level at weaning, whereas the binding in montane voles remained unchanged into adulthood. A sim ilar but opposite pattern was found in the frontoparietal cortex, in w hich AVP receptor binding showed an early peak in montane voles but di d not change significantly in prairie voles. These results demonstrate that 1) species differences in regional AVP receptor binding are evid ent in the early postnatal period and, in several areas, may be determ ined by genetic or prenatal factors, and 2) AVP may target brain areas differently in infant and adult prairie and montane voles and, thus, could exert differential effects on the organization of the central ne rvous system in the two species of voles. (C) 1997 Wiley-Liss, Inc.