Actions of some autonomic drugs on isolated dog quiescent ureter

Actions of some autonomic drugs on upper, middle and lower portion of isolated dog ureters under quiescent state were investigated quantitatively. Noradrenaline and adrenaline at lower concentrations evoked contractions in each portion of the ureters and increased the concentration-dependent frequency and tension of these contractions, but attenuated them at higher concentrations. Phentolamine significantly depressed these contractions, while propranolol enhanced them. Phenylephrine increased the concentration-dependent frequency and tension of contractions, which were suppressed by phentolamine. Acetylcholine at higher concentrations produced contractions of the ureters, and phentolamine or hexamethonium suppressed them. The results indicate that ureteral contractions may be stimulated through an activation of alpha-adrenoceptors and be attenuated through an activation of beta-adrenoceptors, and that acetylcholine may release noradrenaline from sympathetic nerve endings through an activation of presynaptic nicotinic receptors, resulting in ureteral contractions.