The expression of voltage-dependent calcium channel beta subunits in human hippocampus

The beta subunits of voltage-dependent calcium channels (VDCC) modulate the electrophysiology and cell surface expression of pore-forming alpha(1) subunits. In the present study we have investigated the distribution of beta(1),beta(2),beta(3) and beta(4) ill the human hippocampus using in situ hybridization (ISH) and immunohistochemistry. ISH studies showed a similar distribution of expression of beta(1),beta(2) and beta(3) subunit mRNAs, including labelling of the dentate granule cell layer, all CA pyramidal regions, and the subiculum. Relatively low levels of expression of beta(1) and beta(2) subunit mRNAs correlated with low protein expression in the immunocytochemical (ICC) studies. There was a relative lack of beta(4) expression by bath ISH and ICC in the CA1 region, compared with high levels of expression in the subiculum. Immunostaining for beta(1) and beta(2) subunits was weak and relatively homogeneous throughout the hippocampus. The beta(3) and beta 4 subunits appeared to be more discretely localized. In general, beta(3)-immunoreactivity was moderate both in cell bodies, and as diffuse staining in the surrounding neuropil. Strongest staining was observed in mossy fibres and their terminal region in the CA3 stratum lucidum. In contrast, beta(4)-immunoreactivity in the neuropil showed intense dendritic localisation. Unlike the other subunits, beta(4)-immunoreactivity was absent from CA1 pyramidal neurones but was present in a small population of interneurone-like cells. The localisation of beta(3) and beta(4) may represent presynaptic and postsynaptic compartments in some populations of hippocampal neurones. Comparison of beta subunit distribution with previously published data on alpha(1) subunits indicates certain neuronal groups and subcellular compartments in which the subunit composition of native pre- and postsynaptic VDCC can be predicted. (C) 1998 Elsevier Science B.V. All rights reserved.