THE EFFECT OF HYDRALAZINE ON GANGLIONIC TRANSMISSION

¹ Department of Pharmacology, Seton Hall College of Medicine and Dentistry, Jersey City, New Jersey

The effect of hydralazine on transmission through the superior cervical ganglion of the cat was investigated. The drug, when perfused through the gamglion, produced a noticeable block of tratmsmission within 2 hours with concentrations as low as 5 µg/ml (2.54 x 10^-5 M). Higher concentrations blocked tm-more quickly and more completely. The block was found to be qualitatively similar to that of iproniazid and beta-phenylisopropyl hydrazine in that acetylcholine was still released on preganglionic nerve stimulation. In addition, exogenous acetylcholine was as effective in stimulating the ganglion tells during total blockade of transmission as before treatment with hydralazine. The inability of the classical theory of synaptic transmission to explain the nature of the block is discussed. During hydralazine perfusion, the inhibitory effect of tyramine on transmission was potentiated; the stimulatory action of 5-hydroxytryptamine was reversed to inhibition of transmission.