Multiple calcium channels mediate neurotransmitter release from peripheral neurons.

Abstract

We examined the effects of dihydropyridine drugs on evoked neurotransmitter release from cultured neonatal rat sensory and sympathetic neurons. Depolarization with K+-rich solutions increased the release of substance P from cultured sensory neurons. This release was enhanced by BAY K8644 and (+)-202791 and was blocked by a variety of other dihydropyridines including (-)-202791, by Co2+, or in Ca2+-free solutions. K+-rich solutions also stimulated the release of [3H]norepinephrine from cultured sympathetic neurons. This release was also completely blocked by Co2+ or in Ca2+-free solution. In contrast to the situation in sensory neurons, however, the evoked release of [3H]norepinephrine was completely resistant to the blocking effects of dihydropyridine such as nimodipine. However, BAY K8644 was able to enhance the evoked release of [3H]norepinephrine, and this enhancement was blocked by nimodipine. These results are discussed in relation to the possible participation of multiple types of calcium channels in the release of neurotransmitters.