Characteristics of voltage sensitive calcium channels in dendrites of cultured rat cerebellar neurons

We examined the effects of various pharmacological agents on the Ca²⁺ channels existing in the dendrites of cultured rat cerebellar neurons. The cultures consisted of Purkinje cells and non-Purkinje cells (deep cerebellar nuclear neurons and other non-granule neurons). Changes in intracellular free calcium concentration, [Ca²⁺]_i, were monitored by digital imaging microfluorimetry using fura-2 as the indicator dye. In the Purkinje cell population increases in dendritic [Ca²⁺]_i evoked by brief pulses of high K⁺ were very effectively blocked by (> 80%) by ω-Aga-IVA at low concentrations. Nimodipine and ω-conotoxins GVIA and MVIIC only blocked small components of the [Ca²⁺]_i rise. In the non-Purkinje cells, ω-Aga-IVA was much less effective. ω-Conotoxin-GVIA blocked somewhat more and nimodipine blocked a similar percentage of the [Ca²⁺]_i rise. ω-Conotoxin-MVIIC was quite ineffective in these cells. The results are discussed in terms of the types of voltage sensitive Ca²⁺ channels existing in the dendrites of these cells.