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Neuronal associations in the rat suprachiasmatic nucleus demonstrated by immunoelectron microscopy
Author(s) -
Daikoku Shigeo,
Hisano Setsuji,
Kagotani Yasuaki
Publication year - 1992
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.903250408
Subject(s) - immunolabeling , biology , axon , synaptogenesis , neuroscience , synaptic vesicle , suprachiasmatic nucleus , vasopressin , synapse , neuron , microbiology and biotechnology , axon terminal , endocrinology , vesicle , central nervous system , biochemistry , immunohistochemistry , membrane , immunology
The synaptic associations of neurons in the suprachiasmatic nucleus (SCN) of rats were examined by single immunolabeling for somatostatin (SRIH) and arginine vasopressin (AVP), and double immunolabeling for SRIH plus AVP and vasoactive intestinal polypeptide (VIP) plus AVP. Single immunolabeling showed that SRIH neurons, which displayed some somatic and dendritic spines, formed synaptic contacts with immunonegative and positive axon terminals. AVP neurons also formed synaptic contacts with both immunonegative and positive axon terminals. The immunonegative terminals contained small, spherical clear vesicles or flattened clear vesicles. A few immunopositive AVP fibers made synapses with immunonegative somatic or dendritic spines. Double immunolabeling showed synaptic associations between SRIH axons and AVP cell bodies or dendritic processes, and between AVP axons and the somata or dendrites of SRIH neurons. These findings suggest a reciprocal relation between the two types of neurons. Synaptic contacts between AVP neurons and VIP axon terminals were also demonstrated. Previously, we found synapses between SRIH axons and VIP neurons. Thus SRIH neurons appeared to regulate AVP and VIP neurons. On the basis of these findings, two possible oscillation systems of the SCN are proposed. © 1992 Wiley‐Liss, Inc.