0000000000634085
AUTHOR
M.p. D’ocón
Intervention of two voltage-dependent calcium-entry pathways in the contractile response to acetylcholine and KCl in rat uterus.
The contractile response of rat uterine smooth muscle was investigated. Verapamil and diltiazem concentration-dependently relax the sustained contractions induced by KCl (56 mmol/l) or acetylcholine (10(-4) mol/l). This inhibitory effect was not not freely reversed by washing the tissue and subsequently no contractile response was obtained in depolarized tissue, but a lower biphasic response (phasic and tonic) to acetylcholine was observed. Addition of cumulative concentrations of CaCl2 (1.2-19.2 mmol/l) induced a partial recovery of the contractile response to acetylcholine or KCl, but addition of MgCl2 (1.2-19.2 mmol/l did not. When the channel was reactivated by a third addition of KCl o…
Effect of different treatments in calcium-free medium on basal tone and contractile responses of guinea pig tracheae.
Acetylcholine (ACh; 0.1 mmol/l) and KCl (80 mmol/l) induce a biphasic contractile response in isolated guinea pig tracheae maintained at 37 degrees C either in the presence or absence of extracellular Ca2+. Exposure of the tissue to Ca(2+)-free solution evokes a significant decrease in basal tone and the sources of Ca2+ appear to be decreased by prolonged agonist stimulation, and even more by successive agonist stimulation. After an incubation period of 20 min in Ca(2+)-containing solution, the response is restored. Mg(2+)-depletion in Ca(2+)-free medium increased the contractile response to ACh, but not to KCl, and delayed the tonic component of the next contraction elicited in Ca(2+)-cont…
Vasodilator Effects of Liriodenine and Norushinsunine, Two Aporphine Alkaloids Isolated from <i>Annona cherimolia,</i>in Rat Aorta
The effect of two aporphines, liriodenine and norushinsunine, isolated from Annona cherimolia, were studied in the rat aorta in order to examine their mechanism of action. Both alkaloids (10–7–10–4 mol/l) showed relaxant effects on the contractions elicited by 10–6 mol/l noradrenaline (NA) or 80 mmol/l KC1, but, while liriodenine showed a nonspecific relaxant action on both spasmogens, norushinsunine was more potent on KC1-induced contraction. In Ca2+-free medium, both alkaloids (0.1 mmol/l) inhibited the responses elicited by NA, but not those elicited by caffeine. This inhibitory action occurred when the alkaloids were present during the release of the Ca2+ internal stores or during the r…