Effects of hyperpolarization-activated channel blocker ZD7288 on polar excitations of frog sciatic nerve.

Previous studies have demonstrated that Ar(+) laser irradiation shows a more selective blocking effect on the generation of anode-break-excitation (AE) than on cathode-make-excitation (CE), and that the effects of laser irradiation closely resemble those following the application of hyperpolarization-activated current (Ih) blocker, ZD7288. We therefore examined the effects of ZD7288 and tetrodotoxin (TTX) on polar excitations to reveal whether such a selective effect of ZD7288 on AE is specific in frog sciatic nerve. Supramaximal stimuli (10-ms pulse) were applied while for 30 min each channel blocker was applied to the stimulating sites.