In the fifth year of this project, our focus continues to be the ontogency of stress response systems in the brain with a special reference to the role of these systems in the organization of behavior. Last year we described the early and exuberant development of brain corticotropin releasing factor (CRF) receptors in the rat. During this year, we investigated the role of these receptors in the rat pup's behavioral response to social isolation. Central (i.e. intracerebroventricular), but not peripheral, administration of CRF was found to decrease the number of ultrasonic isolation calls in the 8-day-old rat. The number of these calls was increased following central administration of a synthetic CRF antagonist. In related studies, central administration of the same peptides to squirrel monkeys revealed dose-dependent changes in locomotor behavior as well as in several species-typical patterns of vigilance and aggression. We also studied the effects of stress at different stages of development on CRF receptors. Opiate receptors were also measured as these same stress paradigms have been associated with hypalgesia. No alterations in brain CRF receptors were noted although mu opiate receptors decreased in selective regions following stress in either the prenatal or adult periods. Taken together, these results implicate brain CRF receptors in the mediation of several stress-related behaviors. In spite of our earlier discover of profound changes in CRF receptor number and distribution in development, these new results suggest that the numbers of these receptors, either in adulthood or infancy, are not altered by several forms of environmental stress.
