The Journal of Neurophysiology Vol. 78 No. 2 August 1997, pp. 884-890
Copyright ©1997 The American Physiological Society

Voltage-Dependent Gating of ATP-Activated Channels in PC12 Cells

Ken Nakazawa, Min Liu, Kazuhide Inoue, and Yasuo Ohno

Division of Pharmacology, National Institute of Health Sciences, Setagaya, Tokyo 158, Japan

Nakazawa, Ken, Min Liu, Kazuhide Inoue, and Yasuo Ohno. Voltage-dependent gating of ATP-activated channels in PC12 cells. J. Neurophysiol. 78: 884-890, 1997. The possibility that P2X receptors exhibit voltage-dependent gating in a similar manner to nicotinic receptors was investigated in rat pheochromocytoma cells with the use of whole cell voltage-clamp techniques. In the presence of extracellular ATP, slowly activating inward currents were elicited by stepping from 50 mV to potentials more negative than 80 mV; these currents had a time constant of ~60 ms at 120 mV. This slowly activating component (as a fraction of the total ATP-induced current) increased with membrane hyperpolarization from 80 to 100 mV and was much increased when depolarizing prepulses were applied, although the time constant of activation was not altered by depolarizations. The fraction of the slowly activating current and its time constant were decreased as the ATP concentration was increased from 10 to 300 µM. Thus it has been demonstrated that voltage-dependent gating of ATP-activated channels does occur in PC12 cells, and that this gating is modified by agonist concentration. It is possible that such gating may serve as a postsynaptic mechanism to facilitate excitatory neurotransmission by contributing to the inward rectification of the ATP-activated currents.