Effects of thiopental on Ca2+ currents and intracellular Ca2+ transient in single atrial cells from guinea pig.
The effects of thiopental on Ca2+ currents and intracellular Ca2+ transient in single atrial cells from guinea pigs were studied by means of a whole-cell voltage-clamp method and Ca2+-sensitive fluorescent dye. Thiopental inhibited L-type voltage-dependent Ca2+ currents in a concentration-dependent manner (IC50=2.8.10(-5) mol/l). Moreover, the mode of Ca2+ current inhibition by thiopental showed no use dependency. Electrical stimulation-induced intracellular Ca2+ transient was significantly suppressed by 10(-5) mol/l thiopental. However, the caffeine-sensitive Ca2+ releasing pathway from sarcoplasmic reticulum was not affected by thiopental. Our results indicate that thiopental inhibits L-type Ca2+ currents, but not release of Ca2+ from sarcoplasmic reticulum. These results suggest that the negative inotropic action of thiopental is mainly due to inhibition of L-type Ca2+ channels in guinea pig atrial myocytes.
Kimura
Maki
M
Department of Clinical Pharmacy, Faculty of Pharmaceutical Sciences, Toho University, Miyama, Funabashi, Japan.
Shibukawa
Yoshiyuki
Y
Momose
Yasunori
Y
Sugaya
Makoto
M
Yamamura
Shigeo
S
Suzuki
Takashi
T
Hatakeyama
Noboru
N
Yamazaki
Mitsuaki
M
D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000187:drug effects*; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D004558:Electric Stimulation; D004594:Electrophysiology; D006168:Guinea Pigs; D008564:Membrane Potentials / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000187:drug effects; D018408:Patch-Clamp Techniques; D013874:Thiopental / Q000494:pharmacology*
D000927:Anticonvulsants; D015220:Calcium Channels; D000697:Central Nervous System Stimulants; D002110:Caffeine; D013874:Thiopental; D002118:Calcium