Dependence of β‐adrenoceptor mediated mechanical effects on the glycogen concentration in the rabbit isolated small intestine

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

“…Unlike rabbit intestine, responses of mouse ileum to isoprenaline were reduced by phentolamine, and although Hall (1972) described the development of tachyphylaxis to isoprenaline in rabbit intestine, such an explanation is unlikely here since not only did the reported tachyphylaxis take an hour or two to develop but also in our experiments combined aand /8-adrenoceptor blockade was more effective than either antagonist alone.…”

“…All four agonists can activate both types of receptor, since combined a-and 38adrenoceptor blockade caused a greater antagonism than either phentolamine or propranolol given alone, although only the duration and not the amplitude of phenylephrine-induced relaxation was affected by propranolol. Unlike rabbit intestine, responses of mouse ileum to isoprenaline were reduced by phentolamine, and although Hall (1972) described the development of tachyphylaxis to isoprenaline in rabbit intestine, such an explanation is unlikely here since not only did the reported tachyphylaxis take an hour or two to develop but also in our experiments combined aand /8-adrenoceptor blockade was more effective than either antagonist alone.…”