Effect of bunazosin on cardiac sympathetic nerve activity in anesthetized rats

The present study was undertaken to elucidate the effect of selective alpha-1 adrenoceptor antagonist, bunazosin, on sympathetic nerve activity in anesthetized rats. Intravenous administration of bunazosin (10 micrograms/kg) produced a reduction of mean arterial pressure with a significant decrease in heart rate. Accompanied with its hypotension and bradycardia, bunazosin caused a decrease in inferior cardiac nerve activity. On the other hand, renal nerve activity, which reflects vasoconstriction, was not significantly decreased by bunazosin. These findings suggest that bunazosin may possess an anti-tachycardic action resulting from the reduction of cardiac sympathetic nerve activity and that the sympathoinhibitory action of bunazosin may not contribute to its hypotensive action.