Distribution of nifedipine- and omega-conotoxin GVIA-sensitive Ca2+ channels in cultured rat neocortical neurons.

L- and N-type voltage-dependent calcium channels are widely distributed in neurons of the CNS. To investigate their subcellular distributions on CNS neurons, intracellular calcium concentration ([Ca2+]i) increase in response to high potassium ([K+]) solution was detected in primary cultured rat neocortical neurons using the calcium indicator dye Oregon Green with a confocal laser scanning microscope. Extracellular application of 90 mM [K+] solution induced fluorescence increase in a manner dependent on extracellular [Ca2+]. The increase was partially blocked by 10 microM nifedipine, and the reduction was higher in cell bodies compared to dendritic processes. In contrast, omega-conotoxin GVIA reduced the 90 mM [K+] induced fluorescence increase more in the dendritic processes. The results demonstrated the heterogeneous distribution of nifedipine- and omega-conotoxin GVIA-sensitive calcium channels, which may suggest a functional difference in nifedipine- and omega-conotoxin GVIA-sensitive channels in cultured neocortical neurons.