Expression pattern of voltage-dependent calcium channel subunits in hippocampal inhibitory neurons in mice

Different subtypes of voltage-dependent calcium channels (VDCCs) generate various types of calcium currents that play important role in neurotransmitter release, membrane excitability, calcium transients and gene expression. Well-established differences in the physiological properties and variable sensitivity of hippocampal GABAergic inhibitory neurons to excitotoxic insults suggest that the calcium homeostasis, thus VDCC subunits expression pattern is likely different in subclasses of inhibitory cells. Using double-immunohistochemistry, here we report that in mice: 1) Ca(v)2.1 and Ca(v)3.1 subunits are expressed in almost all inhibitory neurons; 2) subunits responsible for the L-type calcium current (Ca(v)1.2 and Ca(v)1.3) are infrequently co-localized with calretinin inhibitory cell marker while Ca(v)113 subunit, at least in part, tends to compensate for the low expression of Ca(v)1.2 subunit in parvalbumin-, metabotropic glutamate receptor 1 alpha- and somatostatin-immunopositive inhibitory neurons; 3) Ca(v)2.2 subunit is expressed in the majority of inhibitory neurons except in calbindin-reactive inhibitory cells; 4) Ca(v)2.3 subunit is expressed in the vast majority of the inhibitory cells except in parvalburnin- and calretinin-immunoreactive neurons where the proportion of expression of this subunit is considerably lower. These data indicate that VDCC subunits are differentially expressed in hippocampal GABAergic interneurons, which could explain the diversity in their electrophysiological properties, the existence of synaptic plasticity in certain inhibitory neurons and their vulnerability to stressful stimuli. (c) 2006 IBRO. Published by Elsevier Ltd. All rights reserved.