The inhibitory action of noradrenaline and adrenaline on acetylcholine output by guinea‐pig ileum longitudinal muscle strip

摘要: 1Noradrenaline and adrenaline reduce the output of acetylcholine by guinea-pig ileum longitudinal strip up to 80%, both in resting conditions after stimulation. The effect is graded with dose, detectable noradrenaline 2 × 10−7 g/ml. Adrenaline approximately 4 times as active noradrenaline, its action being washed out more persistent. 2If high, amines have a proportionately greater their action, dosage increased, basal level, relatively constant from strip, about 10 ng/g/min. 3With stimulation, amine at low frequencies, when per volley than high frequencies. reduced increasing number shocks delivered. There thus appears be volley, order 1–2 ng/g/volley, which can reached either rapid prolonged or treatment these amines. 4If applied during continued stimulation 40/min, depression presence followed an augmented drug withdrawn. magnitude this “overshoot” increases duration exposure. 5Phenylephrine μg/ml. amphetamine 20 output, but isoprenaline 1 μg/ml., dopamine methoxamine were ineffective. 6Phenoxybenzamine increased output. Of two other blocking agents examined, phentolamine had no on ergotamine transiently phenoxybenzamine was not due reaction adrenoceptive muscarinic receptors. 7Phenoxybenzamine, abolished response stimulation. 8In strips obtained animals treated reserpine guanethidine, rise frequencies found. In conditions, still effective. 9Reducing hydroxytryptamine content p-chloro-(±)-phenylalanine did significantly affect output. 10It concluded that nervous networks under normal control sympathetic species presynaptic inhibition mediated α receptors. This implies for tissue dual autonomic control, withdrawal will lead parasympathetic only unopposed also itself enhanced.