Some actions of sympathomimetic amines and their antagonists on mouse superfused ileum.

Superfused segments of mouse ileum exhibited spontaneous movement which Mwere inhibited by sympathomimetic amines. Isoprenaline and adrenaline were approximately equipotent and about 15 times more potent than either noradrenaline or phenylephrine. Supersensitivity developed to all these agents when mice had been 'sympathectomized' with NGF-antiserum or 6-hydroxydopamine and it was more pronounced with the latter treatment. Responses to the amines were reduced by phentolamine and propranolol, alone or in combination, with the exception of phenylephrine, the responses to which were simply shortened in duration after,beta-adrenoceptor blockade. No qualitative changes were evident in the effects of the blocking agents after 'sympathectomy'.