Endocrine Abstracts

Decades of clinical experience and research in human and non-human primates demonstrate that maternal care received early in life strongly influences the development of parenting and other social skills as well as resiliency in the face of stress. Analogous intergenerational effects of maternal nurturing have recently been reported in rats. Adult stress responses (anxiety and hypothalamic-pituitary-adrenal axis activation) are inversely related to the amount of maternal licking and arched-back nursing received during infancy. Also, nursing females lick and arch-back nurse their pups at rates similar to those received from their own mothers. Several lines of experimental evidence indicate that oxytocin is involved in transducing the amount of maternal nurturing received during infancy into adult levels of maternal behavior and stress reactivity. First, central administration of oxytocin antagonist decreases nursing mothers' pup-licking and arched-back nursing, but not other components of maternal behavior. Also, oxytocin knock-out mice exhibit a pup-licking deficit. Second, oxytocin receptor concentrations in areas of the adult brain where oxytocin stimulates maternal behavior or diminishes anxiety are positively related to maternal licking and arched-back nursing received during infancy. Third, daily oxytocin and oxytocin antagonist treatment when they were 2-10 days old respectively increase and decrease mothers' pup-licking indicating that oxytocin activity in young female pups, which may be regulated by pup-licking and possibly arched-back nursing received from their mothers, influences their adult levels of pup-licking. These lines of evidence suggest the following model: oxytocin activity in the rat mother's brain determines her frequencies of pup-licking and arched-back nursing which, in her female pups, influences oxytocin activity in their brains which has developmental effects resulting in central oxytocin receptor expression similar to their mother's and, therefore, similar levels of maternal behavior and anxiety.