Actions of the Slow Channel Activator, Bay‐k‐8644, on the Electrical Activity of 3‐day‐old Embryonic Chick Hearts

Abstract

In order to assess the effects of Bay-K-8644 on electrical activities of young embryonic chick hearts in which the rising phase of the action potential (AP) depends on tetrodotoxin-insensitive slow Na+ currents, slow AP were recorded in spontaneously beating 3-day-old embryonic chick hearts. Bay-K-8644(10(-6) mol/l) caused increases in the maximum rate of rise, amplitude, and duration of the slow AP; there was a slow increase in the spontaneous firing rate. Thus, Bay-K-8644 stimulates Na+ influx through TTX-insensitive slow channels.

The L‐Type Ca2+ and KATP Channels May Contribute to Pacing‐Induced Protection Against Anoxia‐Reoxygenation in the Embryonic Heart Model

“…27 Activation of these channels by anoxia-reoxygenation can also result in Ca 2+ overload associated with arrhythmias and contractile dysfunction in the embryonic heart. 28,29 In chick embryonic cardiomyocytes, BAY-K induces longlasting opening of L-type Ca 2+ channel 30 and increases amplitude and duration of the action potential with a slight positive chronotropic effect, 31,32 which was also observed under our basal conditions. The combination of the atrial tachycardia induced by BAY-K (Table 1) and the prolongation of PR interval ( Fig.…”