Isoprenaline enhances both voltage-dependent Ba2+ and K+ currents in guinea-pig vas deferens.
In the guinea-pig vas deferens, isoprenaline (ISO) can exert significantly enhanced effects on voltage-dependent Ca2+ channel current carried by Ba2+ (IBa) via beta-adrenoceptor activation. Voltage-dependent Ba2+ (IBa) and K+ currents (I K) were recorded in the preparation voltage-clamped in a Krebs solution replaced Ca2+ by Ba2+ (Ba2+ solution) of 36 degrees C. At a holding potential of -40 mV, ISO markedly increased IBa evoked by depolarizing pulses, whereas it also increased I K at a holding potential of -20 mV so as to inactivate Ca2+ channel. This ISO-induced enhancement of IBa seems to be contradictory to the suppression of contraction by beta-adrenoceptor activation in normal Krebs solution.
Akita University College of Allied Medical Science, Japan. hi1218@ipc.akita-u.ac.jp
H
H
Inomata
T
T
Mimata
M
M
Wakui
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001464:Barium / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D007473:Ion Channels / Q000187:drug effects* / Q000502:physiology; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D014649:Vas Deferens / Q000187:drug effects* / Q000502:physiology
D000318:Adrenergic beta-Agonists; D007473:Ion Channels; D015221:Potassium Channels; D001464:Barium; D007545:Isoproterenol