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Spiny calretinin‐immunoreactive neurons in the hilus and CA3 region of the rat hippocampus: Local axon circuits, synaptic connections, and glutamic acid decarboxylase 65/67 mRNA expression
Author(s) -
Martínez Albert,
Ruiz Mònica,
Soriano Eduardo
Publication year - 1999
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(19990222)404:4<438::aid-cne2>3.0.co;2-k
Subject(s) - calretinin , biology , axon , neuroscience , glutamate decarboxylase , hippocampal formation , hippocampus , synapse , immunohistochemistry , biochemistry , immunology , enzyme
We have used the Golgi method and Golgi electron microscopic techniques to analyze the axonal arborization and efferent connections of spiny calretinin‐immunoreactive neurons in the CA3 region and hilus of the rat hippocampal formation. In the hilus, the axons of spiny calretinin‐immunoreactive neurons sent out numerous collaterals that arborized in the hilar region and the molecular layer. In the CA3 region, these axons extended mainly to the stratum radiatum and pyramidal layer but also to the stratum oriens and stratum lacunosum‐moleculare. Axonal varicosities were distributed widely throughout the axonal collaterals. Electron microscopic studies revealed that the axon terminals of spiny calretinin‐immunoreactive neurons established synaptic contacts mainly with dendritic shafts. We next analyzed the expression of glutamic acid decarboxylase (GAD65/67) mRNAs in spiny nonpyramidal neurons that were identified by calretinin immunoreactivity. We found that spiny calretinin‐positive neurons in the CA3 region and hilus of the rat hippocampal formation expressed the two isoforms of GAD: GAD65 and GAD67 mRNAs. These findings show that the spiny calretinin‐immunoreactive neurons of hippocampus give rise to local axonal arborizations, suggesting that they are inhibitory. J. Comp. Neurol. 404:438–448, 1999. © 1999 Wiley‐Liss, Inc.