Mode of action of spasmogens (K, acetylcholine, Ba) and relaxants (isoproterenol, Mn, papaverine) on the excised jejunum of the mouse, particularly in relation to Ca.

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  • マウス摘出空腸における収縮薬Ｋ，アセチルコリン，Ｂａおよびし緩薬イソプロテレノール，Ｍｎ，パパベリンの作用機序，とくにＣａとの関連
  • マウス テキシュツ クウチョウ ニ オケル シュウシュクヤク K , Acetylcholine , Ba オヨビ シカンヤク Isoprterenol , Mn , Papaverine ノ サヨウ キジョ , トクニ Ca ト ノ カンレン

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I. Spasmogens : Evidence has accumulated suggesting that (1) phasic contraction (PC) by K is due mainly to Ca influx and partially to Ca release, whereas PCs by ACh and Ba are due to Ca release, and tonic contractions (TCs) by K, ACh and Ba are maintained by energy-dependent Ca influx, and (2) K utilizes the loosely-bound Ca, ACh utilizes the less loosely-bound Ca, and Ba utilizes both the less loosely and the tightly-bound Ca of the tissue for inducing contraction. II. Relaxants : Summing up the results of various experiments (modification of the relaxing actions by the high K-depolarizing and the Ca-free bath solutions, the relative inhibition of ACh-induced PC and TC by relaxants, and the antagonism patterns of relaxants against the concentration-action curves of exogenous Ca and of PCs by K, ACh and Ba), the following conclusions have been reached. (1) The relaxation by isoproterenol is due to the pseudo-competitive (or functional) inhibition of influx and release of Ca in the muscle cell membrane. (2) The relaxation by Mn is due to competitive inhibition against Ca influx and then against Ca release in the membrane followed by non-competitive inhibition against the reactivity of the muscle contractile system to Ca with increased concentrations. (3) The relaxation by papaverine is due to the non-competitive inhibition against influx and release of Ca in the membrane and then against the reactivity of the contractile system with increased concentrations.

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