ウサギOddi括約筋および十二指腸標本における経壁刺激反応および自律神経薬作用の相違
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Exogenously applied acetylcholine causes contractions, depending on the concentration. The contraction was competitively antagonized by atropine and potentiated by physostigmine. On the other hand, exogenously applied phenylephrine, isoproterenol and norepinephrine resulted in relaxation in both preparations. These relaxations were competitively antagonized by adrenergic alpha and beta blocking agents and their combination, respectively. In both preparations, nicotine caused a transient contraction followed by a relaxation. Pretreatment with physostigmine potentiated the contraction in all cases. In 9 out of 22 of the sphincter preparations, and all those of the duodenum, atropine inhibited the contraction caused by nicotine and converted it to a relaxation. In the remaining 13 cases of the atropine-treated sphincter preparations, however, the nicotine-induced response became triphasic: a relaxation followed by a transient slight contraction and a relaxation. The contraction was significantly inhibited by phentolamine or guanethidine. The relaxation caused by nicotine in the presence of atropine was unaffected by propranolol alone, or its combina-tion with phentolamine, bretylium and guanethidine. In both sphincter and duodenum preparations, transmural stimulation caused a transient contraction followed by a relaxation and inhibition of automaticity. Threshold intensity of stimulation was approximately 10V in both preparations. The maximum contractile tension induced by transmural stimulation increased with stimulation intensity until a plateau was attained at 40V. The increase of maximum tension was also seen with stimulation frequency and pulse duration. The time to peak, duration and tension of contraction and the subsequent relaxation of transmural response were compared between the sphincter and duodenum preparations. No difference was observed in any parameter of the responses. Mechanical responses to transmural stimulation and certain autonomic drugs were compared on the isolated sphincter of Oddi and the duodenum from rabbit. Nicotine response in the presence of atropine was the only qualitative difference observed.
- 社団法人 日本薬理学会の論文