NEURON-GLIA INTERACTION IN THE SUPRACHIASMATIC NUCLEUS - A DOUBLE-LABELING LIGHT AND ELECTRON-MICROSCOPIC IMMUNOCYTOCHEMICAL STUDY IN THE RAT

The morphological interactions between astroglial and neuronal element s were elucidated in the rat suprachiasmatic nucleus (SCN) by light an d electron microscopic immunocytochemistry using antibodies against gl ial fibrillary acidic protein (GFAP), vasoactive intestinal peptide (V IP) and arginine-vasopressin (AVP). Throughout the SCN, particularly i n its ventral portion, GFAP-like-immunoreactive (GFAP-LI) astroglial e lements were found. These astrocytes displaying GFAP-like immunoreacti vity occasionally contained fairly well-developed organelles. Some of these astrocytes were found as satellite cells in close contact with n on-immunoreactive neuronal perikarya and processes. Around the neurons , GFAP-LI astroglial processes were also observed to cover some portio ns of presynaptic and postsynaptic elements. In addition, these astrog lial elements were seen between two neuronal somata and pericytes of b lood capillaries as glial endfeet. By double labeling immunoelectron m icroscopy using antibodies against GFAP/VIP and GFAP/AVP, some portion s of VIP-like-immunoreactive or AVP-like-immunoreactive neuronal somat a and processes were found to be engulfed by GFAP-LI astroglial proces ses. The possible functional roles of the morphological interactions b etween astroglial and neuronal elements are discussed. (C) 1998 Elsevi er Science Inc.