SITES OF ACTION OF CRYSTALLINE TETRODOTOXIN ON SYMPATHETIC NERVOUS SYSTEMS

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Abstract
In the nictitating membrane of the cat, the contractions induced by the electrical stimulations of the pre- and post-ganglionic fibers of the cervical sympathetic nerve were slightly suppressed after the intravenous injection of crystalline tetrodotoxin, 5 [um]/kg. After the intraarterial injection of 5 [um], the responses induced by the stimulations of the pre- and post-ganglionic fibers were suppressed, and the suppression of the stimulation of the preganglionic fiber was superior to that of the postganglionic fiber. A precipitous fall in blood pressure was observed after the intravenous injection of crystalline tetrodotoxin, 5 [mu]g/kg. The pressor actions of norepinephrine and tyramine were not affected. In the vas deferens preparation of the guinea-pig, the contraction induced by the stimulation of the preganglionic fiber of the hypogastric nerve (indirect stimulation) was completely blocked after 30 min. from the administration of crystalline tetrodotoxin, 5 x 10-8 M, but the response induced by the direct stimulation of muscle and the function of nerve trunk were scarcely affected. In the isolated intestine preparation of the rabbit (Finkleman''s method), the pendular movement of the intestine was not affected after the administration of crystalline tetrodotoxin, 5 x 10-8 m. Thirty min. after the administration, the suppression of the pendular movement induced by the electrical stimulation of the mesenteric nerve was abolished. The sites of action of crystalline tetrodotoxin on the sympathetic nerve-smooth muscle preparations are both the ganglion and the nerve ending, and the latter is more sensitive.

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