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 omega-Ap-IVA at low concentrations. Nimodipine and omega-conotoxins GVIA and MVIIC only blocked small components of the [Ca2+]i rise. In the non-Purkinje cells, omega-Aga-IVA was much less effective. Omega-conotoxin-GVIA blocked somewhat more and nimodipine blocked a similar percentage of the [Ca2+]i rise. Omega-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.