[Changes of Isi and Ix in sheep cardiac Purkinje fibers during alpha- and beta- adrenoceptor excitation].
When alpha- and beta- adrenoceptors were activated respectively in sheep cardiac Purkinje fibers, changes of the slow inward current (Isi) and delayed rectifier current (Ix) were studied by using two-microelectrode voltage clamp technique. When beta-receptor was blocked by propranolol, phenylephrine 5.0 x 10(-6) mol/L increased the peak value of Isi from 17.5 to 26 nA (n = 6, P less than 0.05) and prolonged the ms recovery time of Isi from inactivation from 293 +/- 51 ms to 441 +/- 190 (n = 4, P less than 0.05). Phenylephrine had no effect on the delayed rectifier current (Ix). When alpha-adrenoceptor was blocked by phentolamine, isoprenaline of 4 x 10(-7) mol/L increased the peak value of Isi from 27.7 to 40.8 nA (n = 7, P less than 0.05) and had no effect on the kinetics of Isi, but it did increase the tail current (Ix) peak value from 6.7 to 14.4 nA (n = 6, P less than 0.05). The results suggest that alpha- and beta-adrenoceptor agonists differ in their effects on delay rectifier current.
Liu
Y M
YM
Xu
Y Q
YQ
Li
C Z
CZ
Wu
J Y
JY
D000818:Animals; D004594:Electrophysiology; D006329:Heart Conduction System / Q000502:physiology*; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology; D008839:Microelectrodes; D010656:Phenylephrine / Q000494:pharmacology; D011690:Purkinje Fibers / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D012756:Sheep
D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D010656:Phenylephrine; D007545:Isoproterenol