[The function of autonomic receptors in canine ureteral smooth muscle]

I have investigated the effects of autonomic drugs and prostaglandins on in vitro smooth muscle spontaneous contractions and made the quantitative analysis of autonomic receptors in the canine ureter. Ureteral muscle strip cut helically usually generated spontaneous contractions whereas those cut circularly or longitudinally did not generate spontaneous contractions. These results suggest the importance of knowing which direction to cut the ureteral smooth muscle in order to generate spontaneous contractions. Norepinephrine (alpha), phenylephrine (alpha 1), carbachol (muscarinic) and PGF2 alpha caused significant increase in contractile force. Terbutaline (beta 2) and PGE2 caused significant decreases in contractile force, while dobutamine (beta 1) and clonidine (alpha) caused no effect. Autonomic receptor densities were determined using radiology and binding techniques. The number of maximum binding sites (Bmax) of 3H-prazosin (PZ), 3H-yohimbine (YOH), 3H-dihydroaloprenolol (DHA) and 3H-quinuclidinylbenzilate (QNB) were 53.8, 16.9, 11.2 and 5.28 fmol/ml protein, respectively. These data suggest that the contractile responses to adrenergic and cholinergic agonists in the canine ureter are mediated through functional adrenergic (alpha 1, beta 2) and muscarinic cholinergic receptors and that the prostaglandins have a role in the contraction of the canine ureter.