Effect of calcium agonists and antagonists on cerebellar granule cells.
In cerebellar cultures, comprising predominantly granule neurones, dihydropyridine (DHP) Ca2+ agonists were potent stimulators of voltage-sensitive 45Ca2+ uptake. Their effect was maximal in partially depolarized cells; at 15 mM K+e half maximal stimulation occurred at about 5 X 10(-8) M BAY K 8644 and 10(-7) M (+)-(S)-202791. Organic Ca2+ antagonists were effective inhibitors of voltage-sensitive calcium entry into granule cells: the order of potency in blocking uptake induced by sub-maximal concentration of K+ and BAY K 8644 was nifedipine greater than (-)-202791 greater than D600. BAY K 8644 also stimulated the release of glutamate, the transmitter of the granule cells, from depolarized cells. Granule cells are therefore a class of neurones whose responsiveness to organic Ca2+ effectors is similar to that of cardiac and smooth muscle. The discrepant findings on the effect of calcium effectors in various preparations of nervous tissues may thus reflect a differential distribution of voltage-sensitive Ca2+ channels in different neuronal cell types.
D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002132:Calcium Radioisotopes; D002531:Cerebellum / Q000166:cytology / Q000502:physiology; D005971:Glutamates / Q000378:metabolism; D009467:Neuromuscular Depolarizing Agents / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000378:metabolism; D051381:Rats
D002121:Calcium Channel Blockers; D002132:Calcium Radioisotopes; D005971:Glutamates; D009467:Neuromuscular Depolarizing Agents; D018377:Neurotransmitter Agents; D002118:Calcium