Different distribution of nifedipine- and omega-conotoxin GVIA-sensitive Ca2+ channels in rat hippocampal neurons

The distribution patterns of nifedipine- and omega-conotoxin GVIA-sensitive Ca2+ channels in rat primary cultured hippocampal neurons were investigated with a confocal laser-scanning microscope. Cells were loaded with the calcium indicator dye Oregon Green/AM, and the responses to high potassium (90 mM) solution with and without the existence of L- and N-type Ca2+ channel blockers were imaged. In general, extracellular application of high [K+] solution induced a [Ca2+]o-dependent increase of [Ca2+]i in both somata and dendritic processes. The increase was reduced by a N-type channel blocker, omega-conotoxin GVIA, and the reduction was greater in dendritic processes than in somata and proximal dendrites. In contrast, the reduction induced by the L-type calcium channel blocker, nifedipine, was observed evenly all over the neurons. The results demonstrated the heterogeneous distribution of nifedipine- and omega-conotoxin GVIA-sensitive calcium channels in cultured hippocampal neurons.