TOPOGRAPHICAL DISTRIBUTION OF CORTICOTROPIN-RELEASING FACTOR TYPE 2 RECEPTOR-LIKE IMMUNOREACTIVITY IN THE RAT DORSAL RAPHE NUCLEUS: CO-LOCALIZATION WITH TRYPTOPHAN HYDROXYLASE

Corticotropin-releasing factor (CRF) and CRF-related neuropeptides are involved in the regulation of stress-related physiology and behavior. Members of the CRF family of neuropeptides bind to two known receptors, the CRF type 1 (CRF1) receptor, and the CRF type 2 (CRF2) receptor. Although the distribution of CRF2 receptor mRNA expression has been extensively studied, the distribution of CRF2 receptor protein has not been characterized. An area of the brain known to contain high levels of CRF2 receptor mRNA expression and CRF2 receptor binding is the dorsal raphe nucleus (DR). In the present study we investigated in detail the distribution of CRF2 receptor immunoreactivity throughout the rostrocaudal extent of the DR. CRF2 receptor-immunoreactive perikarya were observed throughout the DR, with the highest number and density in the mid-rostrocaudal DR. Dual immunofluorescence revealed that CRF2 receptor immunoreactivity was frequently co-localized with tryptophan hydroxylase, a marker of serotonergic neurons. This study provides evidence that CRF2 receptor protein is expressed in the DR, and that CRF, receptors are expressed in topographically organized subpopulations of cells in the DR, including serotonergic neurons. Furthermore, these data are consistent with the hypothesis that CRF2 receptors play an important role in the regulation of stress-related physiology and behavior through actions on serotonergic and non-serotonergic neurons within the DR. (C) 2011 IBRO. Published by Elsevier Ltd. All rights reserved.