Untersuchungen zur Acetylcholin-Wirkung auf die Vena portae des Meerschweinchens
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Some characteristics of cholinergic effects on the portal vein of the guinea pig
Cholinergic effects on spontaneously active isolated segments of guinea-pig portal vein were studied by long-term intracellular measurements of membrane potential and simultaneous recordings of mechanical activity.
Acetylcholine induces a strengthening of spontaneous activity: a decrease of the basic membrane potential is associated with an increase in spike frequency and a rise in tension. After repeated acetylcholine-applications, a marked tachyphylactic effect was observed.
Reactions to acetylcholine were not affected either by a nerve blocking agent (tetrodotoxin) or by an adrenergic blocking agent (phentolamine).
Reactions to acetylcholine were markedly reduced or abolished by atropine.
The results give evidence of a “muscarinic” mechanism, which means a direct effect of acetylcholine on the membrane of the muscle cells. This indicates the existence of similarities to intestinal muscle and suggests less specificity of the smooth muscle of portal vein.
Key-WordsSmooth Muscle Portal Vein Spontaneous Activity Acetylcholine “Muscarinic” Effect
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