title: 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.
abstract: 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.
authors.affiliation: Department of Anatomy and Neurobiology, Kyushu University Faculty of Medicine, Higashiku, Fukuoka, Japan. toida@a3rd.med.kyushu-u.ac.jp
authors.forename: K
authors.initials: K
authors.lastname: Toida
authors.forename: K
authors.initials: K
authors.lastname: Kosaka
authors.forename: C W
authors.initials: CW
authors.lastname: Heizmann
authors.forename: T
authors.initials: T
authors.lastname: Kosaka
mesh_terms: D000818:Animals; D064092:Calbindin 1; D064026:Calbindins; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D008961:Models, Structural; D009419:Nerve Tissue Proteins / Q000032:analysis*; D009474:Neurons / Q000145:classification / Q000166:cytology* / Q000648:ultrastructure; D009830:Olfactory Bulb / Q000166:cytology*; D051381:Rats; D017208:Rats, Wistar; D064030:S100 Calcium Binding Protein G / Q000032:analysis*; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure*; D005680:gamma-Aminobutyric Acid / Q000032:analysis
chemical_list: C576500:Calb1 protein, rat; D064092:Calbindin 1; D064026:Calbindins; D009419:Nerve Tissue Proteins; D064030:S100 Calcium Binding Protein G; D005680:gamma-Aminobutyric Acid