Immunocytochemical Studies of Corticotropin Releasing Factor-like Immunoreactive Innervation of Atrial Natriuretic Peptide Neurons in the Rat Diencephalon

Synaptic inputs of corticotropin-releasing factor (CRF)-like Immuno reactive axon terminals to neurons containing atrial natriuretic peptide (ANP) in the anteroventral third ventricle (AV3V) region of the rat diencephalon were examined ultrastructurally by a pre-embedding double immunostaining technique combining the silver-gold intensified peroxidase-antiperoxidase complex-3,3'diaminobenzidine (SGI-PAP-DAB) method for ANP with the nonintensified PAP-DAB method for CRF. CRF-like Immunoreactive axon terminals were found to make asymmetrical or symmetrical synaptic contacts with ANP-like Immunoreactive nerve cell bodies and processes in the AV3V region. These findings suggest that CRF-containing neurons may regulate the secretory activity, or other functions, or both, of ANP-containing neurons through synapses in the AV3V region of the rat diencephalon.