[Action of atropine on smooth muscle contractions after administering alpha-adrenoreceptor blockaders]

In acute experiments on anesthetized cats, changes of potentials and motility of the longitudinal and circular layers of the small intestine and stomach were studied in response to atropine administration before and after blocking of alpha--adrenoreceptors (dihydroergotamine, dihydroergotoxin, phentolamine, phenoxybenzamine). The effects of these drugs both on spontaneous and evoked (histamine, i. v., sucrose and NaCl into the gut lumen) motor activity were studied. The inhibitory action of atropine on intestinal motility was partially (in intact animals) or completely (on isolated intestinal segments) abolished after alpha-adrenoreceptor blocking. The mechanism of the atropine effect is discussed in the light of the data on M--cholinoreceptors in the sympathetic postganglionic axons.