Multiple calcium channels mediate neurotransmitter release from peripheral neurons.
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.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D046508:Culture Techniques; D005727:Ganglia, Spinal / Q000502:physiology; D005728:Ganglia, Sympathetic / Q000502:physiology; D007473:Ion Channels / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism; D010525:Peripheral Nerves / Q000502:physiology*; D011188:Potassium / Q000502:physiology; D051381:Rats; D013373:Substance P / Q000378:metabolism
D002121:Calcium Channel Blockers; D007473:Ion Channels; D018377:Neurotransmitter Agents; D013373:Substance P; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine