Neonatal stress transiently alters the development of hippocampal oxytocin receptors.

The development of brain oxytocin (OXT) receptors was examined following the mild stress of daily, 20 min separations of infant rats from their mothers (repeated separation condition) or in undisturbed controls. Changes in OXT receptors were characterized in cell membrane preparations, using the OXT receptor ligand [125I]d(CH2)5[Tyr(Me)2Thr4Tyr-NH9(2)]-ornithine vasotocin ([125I]OTA), from rats at 4, 8, 14, 22 postnatal days of age or as adults. In the hippocampus of control animals, [125I]OTA binding was highest at day 4 or 8 and declined thereafter. Repeated separation decreased the Bmax of [125I]OTA binding in whole hippocampus at day 8, an effect that did not persist into adulthood. This effect was found to be confined to the rapidly proliferating, dorsal hippocampus. It has been suggested that brain OXT is involved in both affiliative/social and stress-related behaviors. While the specific function of OXT receptors in hippocampus is currently unknown, mild stress to the infant and the disruption of infant-mother contact transiently alters the normal development of this system.