Abstract
Here we introduce the behavioral study of the mice lacking oxytocin (OXT) or OXT receptor (OXTR) genes. Oxtr-/- males showed elevation in their aggression, with normal plasma concentration of testosterone. In contrast, Oxt-/- males showed no elevated aggression, demonstrating discrepancy between the functions of oxt and oxtr genes. In detection of remanent receptor activity for OXT, no binding capacity to OXT in brain of Oxtr-/- mice was found. In the receptor mutants, concentration of OXT and AVP in pituitary, and of plasma OXT, and expression level of mRNAs of OXT and AVP in hypothalamus were all not altered. We suspected the influence of maternal OXT through placenta on the development of fetus brain to establish normal social behavior in Oxt-/- male. Oxt-null males from cross of Oxt-null parents, showed elevated aggression, according to our expectation. On the other hand, Oxtr-/- female showed abnormal maternal behavior in retrieving and crouching over the pups. Virgin Oxtr-/- females also displayed a similar defect, suggesting that OXTR is required for nurturing responses to pups outside the physiological context of pregnancy and parturition. In addition, decrease in isolation-induced ultrasonic vocalizations and increase in locomotor activity of infant males, and impairment of social discrimination as well as Oxt-/- were found in Oxtr-/- male. Our study demonstrates that OXTR may play a critical role in regulating several social behaviors, related to developmental psychiatric disorders. [Jpn J Physiol 55 Suppl:S17 (2005)]
