CHARACTERISTICS OF VOLTAGE-SENSITIVE CALCIUM CHANNELS IN DENDRITES OFCULTURED RAT CEREBELLAR NEURONS

We examined the effects of various pharmacological agents on the Ca2channels 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 om ega-Ap-IVA at low concentrations. Nimodipine and omega-conotoxins GVIA and MVIIC only blocked small components of the [Ca2+]i rise. In the n on-Purkinje cells, omega-Aga-IVA was much less effective. Omega-conoto xin-GVIA blocked somewhat more and nimodipine blocked a similar percen tage of the [Ca2+]i rise. Omega-conotoxin-MVIIC was quite ineffective in these cells. The results are discussed in terms of the types of vol tage sensitive Ca2+ channels existing in the dendrites of these cells.