EVIDENCE FOR CORTICOTROPIN-RELEASING HORMONE PROJECTIONS FROM BARRINGTONS NUCLEUS TO THE PERIAQUEDUCTAL GRAY AND DORSAL MOTOR NUCLEUS OF THE VAGUE IN THE RAT

The present study used anterograde and retrograde tract tracing and im munohistochemistry to determine the efferent projections of corticotro pin-releasing hormone (CRH) neurons of Barrington's nucleus in the rat . Injections of Phaseolus vulgaris-leucoagglutinin into Barrington's n ucleus resulted in anterograde labeling in the dorsal motor nucleus of the vagus, periaqueductal gray, medial thalamic nuclei, lateral hypot halamus, paraventricular nucleus of the hypothalamus, lateral preoptic area, and lateral septum. The retrograde tract tracer, fluorogold, in jected into the lumbosacral spinal cord labeled many, but not all, CRH -immunoreactive neurons in Barrington's nucleus. Moreover, some Barrin gton's neurons that were retrogradely labeled from the spinal cord wer e not CRH-immunoreactive. Several CRH-immunoreactive Barrington's neur ons were retrogradely labeled by fluorogold injections into the periaq ueductal gray, and these were located predominantly in the dorsal part of the nucleus. Additionally, some CRH-immunoreactive Barrington's ne urons were retrogradely labeled from fluorogold injections into the do rsal motor nucleus of the vagus. In contrast, fluorogold injections in to the lateral hypothalamus, lateral preoptic area, or lateral septum did not result in double labeling of CRH-immunoreactive neurons in Bar rington's nucleus. These results suggest that many, but not all, CRH-c ontaining neurons of Barrington's nucleus project to the lumbosacral s pinal cord. In addition to their previously documented projections to the spinal cord, these neurons may be a source of CRH in the periaqued uctal gray and dorsal motor nucleus of the vagus. CRH projections of B arrington's nucleus may play a role in behavioral or autonomic aspects of stress responses, in addition to their proposed role in micturitio n. (C) 1995 Wiley-Liss, Inc.