Regulation of intracellular calcium in cerebellar granule neurons: effects of depolarization and of glutamatergic and cholinergic stimulation.
The regulation of the cytosolic free Ca2+ concentration ([Ca2+]i) was investigated by microfluorimetry in single cerebellar granule neurons exposed to various treatments (high K+, glutamate, or acetylcholine) and drugs. The responses to the treatments developed asynchronously during cell culture, with high K+ and glutamate reaching their maxima at 6 and 7 days in vitro and acetylcholine at 9 days in vitro. The biphasic [Ca2+]i transients induced by high K+ (an initial peak, followed by a plateau 30-40% of the peak, both sustained by dihydropyridine-sensitive voltage-gated Ca2+ channels) were dissipated by washing with fresh medium or, more rapidly, by addition of excess EGTA (t1/2 = 11 +/- 2 and 3 +/- 0.6 s, respectively). Compared to those induced by high K+, the [Ca2+]i transients induced by glutamate administered in Mg2(+)-free medium were much more variable. An initial peak, sustained by voltage-gated Ca2+ channels, was visible in only approximately 50% of the cells and disappeared when multiple glutamate pulses were administered. In the rest of the population, the transients were monophasic, with persistent plateaus sustained only in part (30-40%) by voltage-gated Ca2+ channels.(ABSTRACT TRUNCATED AT 250 WORDS)
Ciardo
A
A
Department of Pharmacology, San Raffaele Scientific Institute, University of Milan, Italy.
Meldolesi
J
J
D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology*; D004095:Dihydropyridines / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004594:Electrophysiology; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology*; D051381:Rats; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology
D015220:Calcium Channels; D004095:Dihydropyridines; D005971:Glutamates; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D004533:Egtazic Acid; C038806:1,4-dihydropyridine; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium