In human and non-human primates, decades of clinical and research findings clearly show that nurturing received during infancy and childhood influences the quality of parental and other social behaviors as well as the ability to cope with stress during adulthood. Recent studies of early maternal separation effects in rats demonstrate that postnatal nurturing also shapes adult social behavior and stress responses in lower mammals. This rodent model permits more detailed investigation of the mechanisms underlying these life-long consequences of early experience than is feasible in primates. In Preliminary Studies, rat dams subjected to brief and long daily maternal separations (BMS vs. LMS) during infancy exhibited, respectively, increased and decreased pup-grooming (PG), maternal aggression and lactation-associated declines in anxiety. These behavioral differences were related to contrasting effects of the BMS and LMS procedures on the amount of maternal care dams received from their mothers. Mothers subjected to brief and long daily pup-separations exhibited respectively increased and decreased PG and arched-back nursing (ABN). Preliminary Studies and other recent evidence indicate that central oxytocin (OT) regulates behaviors that differ between rat dams with contrasting postnatal MS experience and these early experiences are associated with significant differences in OT receptors in brain sites where OT exerts these behavioral effects. These findings suggest the following model of MS effects on mothers and their female offspring. Central OT enhances lactating rat mothers' PG and ABN. Daily brief and long pup-separations (BMS and LMS procedures) respectively raise and lower mothers' PG and ABN by increasing and decreasing central OT enhancement of these maternal behaviors. Dams' PG and ABN frequencies subsequently determine the degree of OT regulation of behavior that develops in female offspring, which influences their adult PG and ABN frequencies as well as lactation-associated changes in aggression and anxious behavior. The proposed Experiments will test this model by pursuing five Specific Aims.
Specific Aim 1 is to examine in more detail the relationships between postnatal BMS and LMS and dams' maternal behavior, aggression, lactation changes in anxiety and central OT receptor binding.
Specific Aims 2, 4, and 5 are to determine whether differences in the degree of central OT regulation of PG, ABN, maternal aggression and anxiety contribute to contrasting levels of these behaviors between mothers with postnatal BMS vs. LMS experience. Brain sites in which OT stimulates PG and ABN will also be sought.
Aim 3 is to determine whether upswings and downswings in PG-ABN in mothers subjected to brief and long daily pup-separations are the respective results of increased and decreased OT enhancement of these behaviors.
