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 investigate d with a confocal laser-scanning microscope. Cells were loaded with the cal cium 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+] so lution induced a [Ca2+](o)-dependent increase of [Ca2+](i) in both somata a nd dendritic processes. The increase was reduced by a N-type channel blocke r, omega-conotoxin GVIA, and the reduction was greater in dendritic process es than in somata and proximal dendrites. In contrast, the reduction induce d by the L-type calcium channel blocker, nifedipine, was observed evenly al l over the neurons. The results demonstrated the heterogeneous distribution of nifedipine- and omega-conotoxin GVIA-sensitive calcium channels in cult ured hippocampal neurons. NeuroReport 11:2419-2423 (C) 2000 Lippincott Will iams & Wilkins.