Comparative electrophysiologic effects of @entity8633 , XXXX and @entity3988 in conscious and anesthetized @entity235 .

@entity4485 @entity235 @entity1855 @entity3988 @entity8633 @entity460 @entity1168
The electrophysiologic effects of @entity8633 (10 mg/kg), @entity1855 (0.15 mg/kg) and @entity3988 (0.6 mg/kg) were studied in the chronically instrumented conscious and @entity4485 -anesthetized @entity235 . Sinus node automaticity assessed by the corrected sinus node recovery time and atrio-ventricular conduction assessed by the Wenckebach phenomenon were evaluated by atrial pacing via electrodes placed in the wall of the right atrium, and exteriorized in the neck region. Nineteen @entity235 were studied and groups of 6 @entity235 were used for each experimental session. The @entity460 channel blocking drugs were administered by slow i.v. infusion (15 min). Effects were measured over 45-60 min and compared with the pretreatment value. In conscious @entity235 , heart rate was initially markedly increased by @entity8633 and @entity3988 and only slightly increased by @entity1855 . These chronotropic responses were reversed to @entity1168 by @entity3988 only. Corrected sinus node recovery time measured at the end of infusion was decreased by @entity1855 and @entity3988 and was unchanged by @entity8633 . Lengthening of corrected sinus node recovery time was observed with @entity1855 at the end of the experiment. All 3 @entity460 channel blocking agents produced negative dromotropic responses. To determine to what extent electrophysiologic effects of @entity4485 were involved in the cardiac responses measured in the anesthetized @entity235 , @entity4485 was administered prior to injection of each @entity460 channel blocking agent. @entity4485 produced positive chronotropic and dromotropic effects which were attenuated by the 3 @entity460 channel blocking agents. The reduction of corrected sinus node recovery time induced by @entity4485 was diminished by @entity8633 and @entity3988 and unchanged by @entity1855 . @entity4485 anesthesia thus has important electrophysiologic implications on the effects of @entity460 channel blocking agents on chronotropic and dromotropic variables on the heart.
