The response of the mescnteric vascular circuit of anesthetized dogs to a group of ganglionic blocking agents has ljcen studied. The results demonstmte that these agent-s produce a decrease in blood pressure, blood flow and vasomotor activity of the mesenteric bed and either no change or a decrease in mesenteric resistance. When the perfusing pressure to the mescnteric artery was maintained at control levels an increase in flow with a concomitant decrease in mesenteric resistance followed the injection of the blocking agents. The present report presents experimental evidence that our preliminary report was in error.

The reduction of arterial pressure in anesthetized dogs following the injection of ganglion-blocking agents is dependent primarily upon a reduction in arterial vasomotor activity and secondarily upon a reduction in venous return associated with an increase in vascular capacity. When venous return is maintained at control levels, the administration of the blocking agents of this study invariably produce a decrease in total peripheral resistance (TPR). Ordinarily in the intact animal such a decrease in TPR is not observed due to a marked reduction in cardiac output which produces a secondary increase in TPR. The results of this study further suggests that the venous and arterial systems may differ in their sensitivity to the effects of ganglion-blocking agents.

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