title: Dependence of cytoplasmic calcium transients on the membrane potential in isolated nerve endings of the guinea pig.
abstract: The relation of changes in internal, free Ca2+, measured with arsenazo III, to the membrane potential, measured with the cyanine dye di-S-C2(5) or 86Rb+ distribution ratio, was studied in isolated guinea pig cortical nerve endings. Depolarization of the plasma membrane with veratridine or gramicidin as well as addition of ionophore A23187 led to an increase in cytosolic Ca2+. Only the response to veratridine was inhibited by tetrodotoxin. The dependence of the depolarization-induced increase in intraterminal, free Ca2+ on the membrane potential between about -50 to 0 mV was sigmoidal. A maximal increase in cytosolic Ca2+ was reached when the membrane potential was depolarized from the resting level, about -64 mV, to about -40 mV. These results show that in isolated nerve endings the activation of voltage-sensitive Ca2+ channels concomitantly leads to an increase in cytosolic, free Ca2+. Comparison of the results of the present study with the previous electrophysiological observations indicate that Ca2+ channels in synaptosomes, presynaptic nerve terminals of the squid giant synapse and cardiac cells have essentially similar voltage dependency.
authors.forename: E
authors.initials: E
authors.lastname: Heinonen
authors.forename: K E
authors.initials: KE
authors.lastname: Akerman
authors.forename: K
authors.initials: K
authors.lastname: Kaila
authors.forename: I G
authors.initials: IG
authors.lastname: Scott
mesh_terms: D000818:Animals; D001150:Arsenazo III; D002118:Calcium / Q000502:physiology*; D002232:Carbocyanines; D002540:Cerebral Cortex / Q000502:physiology; D005456:Fluorescent Dyes; D006096:Gramicidin / Q000494:pharmacology; D006168:Guinea Pigs; D008564:Membrane Potentials; D009411:Nerve Endings / Q000502:physiology*; D013574:Synaptosomes / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology; D014701:Veratridine / Q000494:pharmacology
chemical_list: D002232:Carbocyanines; D005456:Fluorescent Dyes; D006096:Gramicidin; D001150:Arsenazo III; D013779:Tetrodotoxin; D014701:Veratridine; D002118:Calcium