Aspects of tonus modulation in guinea pig tracheal muscle

We have studied the tonus of the tracheal muscle (tracheal spiral) gathered from guinea pig and kept in Tyrode solution at 38 degrees C, continuously oxygenated. Tonus variations were recorded by a tension transducer on an xy recorder. After administration of histamine (H) in the organ bathroom, we observed an increase of tonus, with large spontaneous movements of the tracheal muscle. Blocking the beta-adrenergic receptors with propranolol (Pr) suppressed the effect of adrenaline (Adr) but did not influence the effects of II and acetylcholine (Ach) The reaction to II was more diminished in the presence of fosfobion (ATP) in the organ bathroom.