Localization of mRNAs of voltage-dependent Ca2+-channels: four subtypes of α1- and β-subunits in developing and mature rat brain
Abstract The heterogeneous gene expression for four subtypes of al (A,B,C,D)- and β (β1,β2,β3,β4)-subunits of voltage-dependent calcium channels was demonstrated in developing and adult rat brain by in situ hybridization histochemistry. In the adult rat brain the gene expression for A- and B-subtypes was predominant in the cerebellar cortex and hippocampal neuronal layers, with the A-subtype expressed most intensely in the Purkinje cells, while the expression for C- and D-subtypes was predominant in the olfactory mitral and granule cells and the dentate granule cells. The expression of β1-mRNA was prominent in the olfactory mitral cells and dentate granule cells whereas that of β2-mRNA was evident in the hippocampal neuronal layers and cerebellar Purkinje cells. The expression of β3-mRNA was prominent in the olfactory mitral and internal granule cells and medial habenula, whereas that of β4-mRNA in the olfactory mitral cells and cerebellar Purkinje and granule cells. Comparison between the expression patterns for individual α- and β-subunits suggests that the β4-subunit contributes to P-type channel, whereas the β1- and β3-subunits contribute respectively to D- and C-subtypes of L-type channels, although dissociation in the expression patterns were also noted in several brain regions. In addition to neuronal populations, the gene expression for the C-subtype of L-type channel was detected at substantial level in glial cells. In developing brains, the genes for the all subtypes of α1- and β-subunits were expressed in the mantle zones, but not the ventricular zones, of the entire neuraxis and the expression was more or less attenuated during early postnatal periods in most of the brain regions except for the olfactory bulb. hippocampas and cerebellar cortex, suggesting that the Ca 2+-channels are intimately involved in the neuronal differentiation.