Cyclic AMP-dependent modulation of N- and Q-type Ca2+ channels expressed in Xenopus oocytes.
Xenopus oocytes were used for investigating the cAMP-dependent modulation of N- and Q-type Ca2+ channels. Treatments to increase intracellular cAMP concentration with forskolin (FK) and 3-isobutyl-1-methylxanthine (IBMX) markedly potentiated Q-type Ca2+ channel current in oocytes coexpressing alpha 1A and beta subunits, and the enhancement was reversed by protein kinase A inhibitors. Moderate enhancement was observed by FK+IBMX in N-type channel current, of which potentiation was equivalent to that of endogenous Ca2+ channel current being activated by exogenously-expressed beta subunits. No potentiation was observed in the oocyte-native Ca2+ channel current. These results suggest that Q-type Ca2+ channels are more susceptible to the protein kinase A-mediated facilitation than N-type channels. A significant role of Ca2+ channel beta subunits for the cAMP-dependent positive modulation was also suggested.
Department of Pharmacology, Faculty of Pharmaceutical Sciences, Kyoto University, Japan.
K
K
Fukuda
S
S
Kaneko
N
N
Yada
M
M
Kikuwaka
A
A
Akaike
M
M
Satoh
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000502:physiology*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D014981:Xenopus
D015220:Calcium Channels; D004791:Enzyme Inhibitors; D005576:Colforsin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D015056:1-Methyl-3-isobutylxanthine