PT - JOURNAL ARTICLE AU - Martin M. Winbury TI - COMPARISON OF THE VASCULAR ACTIONS OF 1,1-DIMETHYL-4-PHENYLPIPERAZINIUM AND TETRAMETHYLAMMONIUM DP - 1958 Sep 01 TA - Journal of Pharmacology and Experimental Therapeutics PG - 25--34 VI - 124 IP - 1 4099 - http://jpet.aspetjournals.org/content/124/1/25.short 4100 - http://jpet.aspetjournals.org/content/124/1/25.full SO - J Pharmacol Exp Ther1958 Sep 01; 124 AB - The vascular actions of 1,1-dimethyl-4-phenylpiperazinium (DMPP) and tetramethylammonium (TMA) were compared in anesthetized dogs. Intravenous injection of both agents produced an initial transient fall in blood pressure followed by a more prolonged rise in pressure. Hexamethonium blocked both phases of the DMPP action but the hypotensive phase of TMA persisted; this was subsequently blocked by atropine. The hypotensive phase of both compounds was selectively blocked by atropine whereas the hypertensive phase of both compounds was selectively locked by Regitine. Intraarterial injection of TMA into the hind limb produced local vasodilation which was blocked by atropine but not by hexamethonium. DMPP most frequently produced local vasodilation on intraarterial injection but vasoconstriction was observed in a few animals at the start of the experiment. This later changed to vasodilatation. The dilator response to DMPP was blocked or converted to a constrictor response by hexamethonium, Regitine and Ilidar, but not by atropine. Acute denervation of the limb did not alter the response to DMPP or TMA. The results indicate that TMA can stimulate both at the autonomic ganglia and at the peripheral cholinergic effector sites (cholinomimetic action). The mechanism of the local vasodilator action of DMPP is not clear except that it is located in the periphery. It was suggested that it may involve peripheral ganglion cells, an axon reflex or direct stimulation of the smooth muscle in the vessel walls.