Caffeine- and ryanodine-sensitive Ca2+ stores in cultured guinea pig myenteric neurons.
In single fura 2-loaded myenteric neurons, caffeine caused concentration-dependent increases in intracellular Ca2+ concentration ([Ca2+]i) that were quantal, saturable, and reversible. Inhibition of caffeine-induced Ca2+ release was demonstrated by ryanodine (1 microM), dantrolene (10 microM), and procaine (5 mM). Caffeine and cyclopiazonic acid (30 microM) released overlapping Ca2+ stores, whereas the caffeine-releasable pool was a subset of Ca2+ released by the Ca2+ ionophore ionomycin (4 microM). Both mild depolarization (7.5 mM KCl) and a submaximal concentration of caffeine (1 mM) produced neuronal [Ca2+]i oscillations in one-third of cells examined, which could be abolished by ryanodine (1 microM) or removal of extracellular Ca2+. Release of caffeine-sensitive Ca2+ stores induced influx of extracellular Ca2+. Immunolocalization using confocal microscopy revealed ryanodine receptor-like staining within the cytosol of cultured myenteric neurons.
Kimball
B C
BC
Department of Surgery, University of Michigan, Ann Arbor 48109-0331, USA.
Yule
D I
DI
Mulholland
M W
MW
D000818:Animals; D000911:Antibodies, Monoclonal; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002478:Cells, Cultured; D003620:Dantrolene / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D005470:Fluorometry; D006168:Guinea Pigs; D007150:Immunohistochemistry / Q000379:methods; D007425:Intracellular Membranes / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism; D009197:Myenteric Plexus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D011343:Procaine / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology*; D019837:Ryanodine Receptor Calcium Release Channel; D013194:Staining and Labeling
D000911:Antibodies, Monoclonal; D015220:Calcium Channels; D009124:Muscle Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D012433:Ryanodine; D002110:Caffeine; D011343:Procaine; D003620:Dantrolene; D002118:Calcium