Voltage-sensitive calcium channels mediate calcium entry into cultured mammalian sympathetic neurons following neurite transection

Abstract

Calcium ion entry following mechanical neurite transection was examined in cultured sympathetic neurons loaded with the Ca 2+ indicator fluo-3. Neurite transection produced a rapid [Ca 2+] i rise in the cell soma which preceded any [Ca 2+] i rise in the neurite ( n = 30). Blocking sodium channels with tetrodotoxin had no effect on the Ca 2+ rise, but inactivating voltage-sensitive Ca 2+ channels by bath-applying 140 mM potassium prior to the transection, and the simultaneous application of nimodipine and co-conotoxin G VIA, blockers of L-type and N-type Ca 2+ channels, respectively, considerably attenuated the Ca 2+ rise in the soma and neurites. These data contradict the intuitive hypothesis that Ca 2+ entry following mechanical neurite transection occurs via non-specific influx pathways produced by cell-membrane disruption and provide direct evidence in mammalian neurons that immediate, traumatically-induced, increases in neuronal [Ca 2+] i are amenable to pharmacological manipulation.