A ganglion-blocking action of surugatoxin from the Japanese ivory shell (Babylonia japonica)

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  • バイ貝Babylonia japonicaから単離されたSurugatoxinの自律神経節遮断作用
  • バイガイ Babylonia japonica カラ タンリ サレタ Surugatoxin ノ ジリツ シンケイセツ シャダン サヨウ

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Abstract

Pharmacological properties of the surugatoxin from Japanese ivory shell (Babylonia japonica) (Kosuge et al. 1972, Gohgi et al. 1973) were studied, and its properties were compared with those of IS-toxin (Hirayama et al. 1970, 1972, Gohgi et al. 1973) isolated from the same shell. Surugatoxin (0.15_??_0.2mg/kg i. v.) reduced spontaneous movement, causing a drowsiness, mydriasis and relaxation of nictitating membrane in cats. The toxin had no effects either on the neuromuscular junctions or on the striated and smooth muscles. Contractile responses of the guinea-pig ileum preparations to nicotine (1×10-7g/ml) were observed, and the responses to nicotine were abolished by hexamethonium (C6, 4×10-4g/ml). Surugatoxin, on the other hand, at a concentration of 1×10-7_??_1×10-6g/ml reduced or eliminated the responses to nicotine and to 1, 1-dimethyl-4-phenylpiperazium iodide (DMPP, 1×10-6g/ml), but the contractile responses due to 4-(m-chlorophenyl-carbomyloxy)-2-butynyltrimethylammonium chloride (McN-A-343, 1×10-5g/ml) were scarcely effected by the toxin at the same concentrations. The toxin was assumed to have a ganglionic blocking action in the inner plexus of the intestine. Accordingly, effect of the toxin on the superior cervical sympathetic ganglion of cats was studied using the Trendelenburg method (1954, 1956). Surugatoxin injected into the femoral vein (150_??_200μg/kg) or the lingual artery (40_??_50μg/kg, to the ganglion) decreased or abolished the contractile responses of the nictitating membrane and the post-ganglionic external potentials to an electrical stimulation of the pre-ganglionic nerve. Surugatoxin did not however, alter responses to the post-ganglionic nerve stimulation. Injection of surugatoxin (40_??_50μg/kg, to the ganglion) reduced or eliminated contractions of the nictitating membrane due to 2μg/kg of DMPP (to the ganglion), a nicotinic ganglionic stimulant (Chen et al. 1951, 1953) and to 25μg/kg of candicine, a ganglionic stimulant (Urakawa et al. 1959, Deguchi et al. 1963), while the contractions due to 2.5_??_5μg/kg of McN-A-343 (to the ganglion), a muscarinic stimulant (Raszkowski, 1961) were scarcely effected by the toxin with the same dose. When 40_??_50μg/kg of surugatoxin was administered (to the nictitating membrane), it affected neither the responses of nictitating membrane nor the pressor responses of systemic blood pressure induced by norepinephrine (5μg/kg, to the nictitating membrane). The potency of surugatoxin, determined in a manner similar to that described by Gyermek (1957) was about 6 times as strong as that of hexamethonium. It is suggested, that the mode of ganglioplegic action of the surugatoxin is similar to that of IS-toxin (Hirayama et al. 1972), which may be due to an inhibitory action on the nicotinic ganglionic receptors in the inner plexus of the intestine and in the superior cervical nerve. Surugatoxin may be a specific inhibitor on the nicotinic ganglionic receptors in autonomic ganglia.

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