POTENTIATION BY TETRAETHYLAMMONIUM OF THE RESPONSE OF THE CAT SPLEEN TO POSTGANGLIONIC SYMPATHETIC NERVE STIMULATION

¹ Department of Experimental Medicine, F. Hoffmann-La Roche & Co. Ltd., Basle, Switzerland

In the isolated perfused spleen of the cat the contractile response and the norepinephrine output resulting from sympathetic nerve stimulation were greatly increased by tetraethylammonium (TEA). The increased norepinephrine output does not seem to result from interference with norepinephrine uptake into sympathetic nerve endings as in the case of cocaine, but it is most probably due to the increased liberation of norepinephrine by sympathetic nerve impulses as suggested by the findings that a) TEA did not inhibit the removal of norepinephrine infused into the arterial inflow of the spleen, and b) TEA—in contrast to cocaine—increased the amount of norepinephrine predominantly in the first fraction of the venous effluent collected during and after sympathetic stimulation. The increased contractile response results mainly from augmented transmitter liberation, but in addition a postjunctional effect of TEA has to be postulated, since TEA increased the changes in splenic vascular resistance to injected norepinephrine 2 to 4 times in spite of the absence of any effect on norepinephrine inactivation. Studies of the electrical activity of splenic nerves support the assumption that TEA increases the amount of norepinephrine liberated as the result of sympathetic nerve stimulation by lengthening the duration of the action potential.