[Adrenergic reactivity of the gastro-intestinal tract. II. Colon of the guinea pig and cecum of the mice].

A study has been made of the alpha- and beta-adrenoreceptors in the guinea pig colon and the mouse caecum using noradrenalina as agonist and alpha- and beta-adrenolytics separately or together. In the guinea pig colon alpha-adrenolytics used alone did not alter the action of noradrenalin: one beta-lytic (propranolol) used alone has slight non dose-dependent action. The alpha-lytics used together with beta-lytic strongly potential their effect. These results are interpreted as indicating that the preparation contains alpha-receptors as well as beta-receptors; activation of the alpha-receptors is observed only when the beta-mimetic effect of noradrenalin is inhibited. In the mouse caecum alpha-lytics prove devoid of effect either alone or when associated with beta-lytics; it is deduced therefore that this preparation contains only beta-receptors.