Corticotropin-releasing factor receptor type 1 colocalizes with type 2 in corticotropin-releasing factor-containing cellular profiles in rat brain.

OBJECTIVES: To investigate whether CRHR1 and CRHR2 are colocalized in CRH-specific neurons in rat brain.

METHODS: Double/triple immunofluorescence, and combined in situ hybridization were performed in the PVN, amygdala and hippocampus, and triple immunofluorescence was applied to the median eminence (ME), dorsal raphe (DR) and locus coeruleus (LC).

RESULTS: Both CRHR1 and CRHR2 immunoreactivity were highly coexpressed in the PVN, central nucleus of the amygdala (CeA) and hippocampus. Triple immunofluorescence under confocal microscopy confirmed that CRHR1 and CRHR2 are coexpressed in CRH-producing neurons in these regions. The results of in situ hybridization combined with double immunofluorescence further strengthened the finding that CRHR1 and CRHR2 were coexpressed in CRH-specific neurons in the PVN, CeA and hippocampus. In addition, CRH immunoreactivity signals were evidently distributed in the ME, DR and LC, and were coexpressed with both receptors.

CONCLUSION: CRH receptors colocalize in CRH-containing neurons in the PVN, CeA and hippocampus, and CRH, CRHR1, and CRHR2 coexist in the DR and LC. Our results implicate CRHR1 and CRHR2 in coordinating the regulation of CRH neuronal activity in stress and behavioral responses.