Actions of Some Autonomic Drugs on Spontaneous Contractions of Isolated Dog Ureter

Abstract

Effects of some autonomic drugs on the isolated dog ureteral preparations showing spontaneous contractions were investigated quantitatively. Noradrenaline, adrenaline and phenylephnne produced increases in frequency and tension of the contractions which were reversed to decreases or depressed by phentolamine. Isoproterenol abolished the spontaneous contractions. Acetylcholine did not significantly change frequency and tension of the contractions. The results indicate that ureteral spontaneous contractions may be enhanced through an activation of Α-adrenoceptors and be attenuated through an activation of Β-adrenoceptors. However, acetylcholine will not display an important role on the ureteral contractions.

Noradrenaline modulates smooth muscle activity of the isolated intravesical ureter of the pig through different types of adrenoceptors

“…These changes were accompanied by an increase in the rate of fluid transport (Kondo et al, 1985;Morita et al, 1987). Furthermore, Yano et al (1984) confirmed this relaxant response of isoprenaline on canine isolated ureteral preparations. These data agree with those found in other structures of urogenital tract such as oviduct, where the stimulation of Padrenoceptors facilitates the transport of the ovum or embryon (Isla et al, 1989).…”

“…Moreover, Yano et al (1984) showed that phentolamine reversed the increased responses induced by noradrenaline to the inhibitory ones in dog isolated middle ureters.…”

“…Phasic activity might be the consequence of the electrical spikes generated by the renal pacemaker (Mostwing, 1986;Thulesius et al, 1986). Thus, Thulesius et al (1986) found spontaneous contractions in all preparations from intrarenal extension of the ureter, while the spontaneous activity in segments of the dog middle ureter was 49% (Yano et at., 1984). Therefore, the rare spontaneous activity found in our preparations might be ascribed to the distance from the intravesical ureteral segments to the renal pacemaker.…”

Comparative Effects of Diltiazem and Glycerol Trinitrate on Isolated Ureter and Coronary Artery of the Dog

“…In the present study, isolated dog ureters with out spontaneous activity were used as experi mental models, in which rhythmic contrac tions were evoked by an administration of potassium or phenylephrine to confirm parti cipation of calcium influx in the generation of such contractions. The former depolarizes cell membranes [13], and the latter stimu lates adrenergic ct-receptors in smooth mus cle [7,8]. The present observations of evoked ureteral contractions had a rhythm with regu larity and amplitude suggesting that ureteral smooth muscle possesses pace-making prop erties even if short strips of a length of 15 mm are used.…”

“…Only some ureteral preparations showed spontaneous contractions [7,8], The present study was carried out on preparations with out spontaneous activity, and the ureteral rhythmic contractions were induced by an addition of potassium (1.5 X 10'2A/) or phenylephrine (3 X 10_5M). Stable rhyth mic contractions continued for 1.5-2.0 h or more.…”