Central administration of oxytocin modulates the infant rat's response to social isolation.

Several lines of evidence suggest that oxytocin modulates the formation and maintenance of social bonds. In the current experiments we investigated the influence of centrally and peripherally administered oxytocin on the behavior of 6-8 day old rat pups during brief periods of social isolation. Ultrasonic vocalizations emitted by isolated pups were decreased following i.c.v. administration of oxytocin, at doses (500, 1000 ng) which did not affect motor activity. S.c. administered oxytocin (1, 10 micrograms) produced a biphasic change in ultrasonic vocalizations, depending on dose. Central administration of the oxytocin antagonist (d(CH2)5[Tyr(Me)2, Thr4, Tyr-NH2(9)]OVT) (OTA, 500 ng) did not measurably affect pup behavior by itself but did block the decrease in calls following central but not peripheral administration of oxytocin. These data demonstrate that oxytocin via its central receptor can regulate the response to social isolation.