Cyclic AMP elicits biphasic current whose activation is mediated through protein phosphorylation in snail neurons.
The involvement of protein phosphorylation in cAMP-induced transmembrane current was tested electrophysiologically and pharmacologically in identified neurons of the Japanese land snail, Euhadra peliomphala. Intracellular injection of cAMP elicited a biphasic transmembrane current (cAMP current) which consisted of inward and outward components. The inward component was blocked with Na(+)-free, Ca2(+)-free saline and the outward component abolished by either application of tetraethylammonium or a long-lasting exposure to caffeine in Ca2(+)-free saline. The cAMP current was completely suppressed by the protein kinase inhibitors, protein kinase inhibitor isolated from rabbit muscle or isoquinoline sulfonamide (H-8). The catalytic subunit of cAMP-dependent protein kinase transiently restored the cAMP current suppressed by H-8 nearly to pre-H-8 level. These findings suggest that protein phosphorylation may be an intermediate step in the activation process of the cAMP current.
Watanabe
K
K
Department of Physiology, Gifu University School of Medicine, Japan.
Funase
K
K
D000818:Animals; D002118:Calcium / Q000502:physiology; D000242:Cyclic AMP / Q000494:pharmacology*; D004594:Electrophysiology; D007473:Ion Channels / Q000187:drug effects*; D007546:Isoquinolines / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D047428:Protein Kinase Inhibitors; D012908:Snails / Q000502:physiology*; D012964:Sodium / Q000502:physiology
D007473:Ion Channels; D007546:Isoquinolines; D009419:Nerve Tissue Proteins; D047428:Protein Kinase Inhibitors; C053177:N-(2-(methylamino)ethyl)-5-isoquinolinesulfonamide; D012964:Sodium; D000242:Cyclic AMP; D011493:Protein Kinase C; D002118:Calcium