Endogenous oxytocin is involved in short-term olfactory memory in female rats

To investigate the involvement of oxytocin in their short-term lasting olfactory memory performance, adult female Wistar rats (n = 12) were tested for their juvenile discrimination abilities. As measured by their exploratory behavior towards juveniles, the adult rats were able to discriminate between a previously exposed juvenile and a novel one as long as the interval between the two exposures was less than 180 min. This ability was maintained across all days of the estrous cycle and was unaffected by intracerebroventricular administration of synthetic oxytocin (1 ng/5 microl Ringer's solution) or Ringer's solution immediately after the first exposure. However, treatment with the oxytocin receptor antagonist des-Gly-NH2 d(CH2)5[Tyr(Me)2Thr4]OVT interfered with the ability to establish this kind of olfactory memory although the vasopressin V1 receptor antagonist d(CH2)5Tyr(Me)AVP (100 ng/5 microl each) via the same route did not. This suggests that within a narrow range of concentrations endogenous oxytocin, but not vasopressin, is critically involved in short-term olfactory memory for juvenile conspecifics in female rats. These data are discussed in the light of sexual dimorphic brain development.