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Chemically defined neuron groups and their subpopulations in the glomerular layer of the rat main olfactory bulb: III. Structural features of calbindin D28K‐immunoreactive neurons
Author(s) -
Toida Kazunori,
Kosaka Katsuko,
Heizmann Claus W.,
Kosaka Toshio
Publication year - 1998
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/(sici)1096-9861(19980309)392:2<179::aid-cne3>3.0.co;2-#
Subject(s) - calbindin , biology , olfactory bulb , axon , synaptic vesicle , soma , neuroscience , postsynaptic potential , confocal , synapse , electron microscope , olfactory system , anatomy , biophysics , central nervous system , vesicle , immunohistochemistry , biochemistry , receptor , geometry , mathematics , physics , membrane , optics , immunology , genetics
The present study analyzed three‐dimensional structural features and synaptic contacts of morphologically and chemically identified calbindin D28K‐immunoreactive neurons in the glomerular layer of the rat main olfactory bulb by means of combined confocal laser scanning light microscopy, high‐voltage electron microscopy and electron microscopic serial section/three‐dimensional reconstruction. Most of calbindin D28K‐immunoreactive neurons were identified as the periglomerular cell type by combined high‐voltage electron microscopic and confocal laser scanning light microscopic observations, and the minority were the short‐axon cell type and others. The combined confocal laser scanning light microscopic and electron microscopic study revealed that the calbindin D28K‐immunoreactive neurons exhibited unique synaptic contact patterns; they received asymmetrical synapses from presumed mitral/tufted dendrites and made conversely symmetrical synapses with them. About 30% of asymmetrical postsynaptic sites and about 40% of symmetrical presynaptic sites formed reciprocal pairs of synapses. Calbindin D28K‐immunoreactive dendrites and somata also received synapses from GABA‐like‐immunoreactive profiles containing numerous pleomorphic, and a few dense‐cored, vesicles. On the other hand, surprisingly, calbindin D28K‐immunoreactive neurons had almost no synaptic contacts from olfactory nerve terminals. The present study clearly revealed that calbindin D28K‐immunoreactive neurons are a type of periglomerular cell involving unique synaptic contacts that have not been reported so far, and thus indicated that so‐called periglomerular cells should be heterogeneous in their synaptic connections as well as in their chemical and structural features. J. Comp. Neurol. 392:179–198, 1998. © 1998 Wiley‐Liss, Inc.