Adenosine slows cardiac pacemaker activity directly by activating a time-independent potassium current and indirectly by inhibiting isoprenaline-enhanced calcium and pacemaker currents.
Whole-cell and patch clamp techniques have been applied to cells isolated from the rabbit sino-atrial (S-A) node to study the ionic mechanism(s) of adenosine-induced slowing of cardiac pacemaker activity. 2. Viable spontaneously active cells were isolated from the central region of the S-A node of the rabbit heart by an enzymatic dispersion procedure similar to that reported by Giles Kurachi, Nakajima however, after If was enhanced by isoprenaline, adenosine markedly inhibited it. 7. These results provide explanations for both the direct and the indirect effects of adenosine in mammalian cardiac pacemaker tissue: activation of IK(ADO), and of a time-independent background potassium current and inhibition of ICa and If, respectively. Since it is known that there is significant adrenergic tone in the mammalian S-A node both the indirect and the direct effects of adenosine may be of physiological importance.
Belardinelli et al. (Tue,) conducted a other in Cardiac pacemaker activity (rabbit S-A node cells). Adenosine vs. Control / basal state was evaluated on Ionic mechanisms of adenosine-induced slowing of cardiac pacemaker activity. Adenosine slows cardiac pacemaker activity directly by activating a time-independent potassium current and indirectly by inhibiting isoprenaline-enhanced calcium and pacemaker currents.