The adrenergic neurone blocking action of [2-(methylphenylamino)ethyl]guanidine sulfate. I.

Abstract

The effect of [2-(methylphenylamino)ethyl]guanidine sulfate (MPG) on sympathetic nervous system was studied and the following results were obtained : 1) intravenous injection of MPG caused a fall of blood pressure and sustained contraction of the nictitating membrane in urethane anesthetized cat, 2) MPG caused a lasting depression of many excitatory responses, evoked by electrical stimulation of the peripheral sympathetic nerves, that is, inhibition of the response of the cat nictitating membrane to postganglionic sympathetic nerve stimulation and inhibition of the pressor responses in cat to the celiac ganglion or splanchnic nerve stimulation. In addition, these reduced responses were abolished by amphetamine, 3) MPG also caused the potentiation of the pressor responses to norepinephrine and epinephrine, but caused a potent antagonistic action to pressor responses produced by tyramine, dimethylphenyl-piperazinium and the occulusion of the carotid artery in cat, 4) injection of high doses of MPG caused a sympathomimetic effect on the cat nictitating membrance, the heart rate of cat and dog and the blood pressure in spinal cat. The contraction of the cat nictitating membrane by MPG was abolished by phentolamine and pretreatment with reserpine. From the results mentioned above, it is concluded that MPG has adrenergic neurone blocking action and sympathomimetic action resembling those of guanethidine and bretylium.