Search results for "Verapamil"
showing 10 items of 68 documents
Antagonism of calcium by zinc in guinea-pig isolated taenia caeci and trachealis muscle
1989
1 In guinea-pig isolated taenia caeci and trachealis bathed in a K+-rich, Ca2+-free medium, CaCl2 (0.01-10 mM) produced a concentration-dependent contraction. Zn2+ (0.01-1 mM), Cd2+ (0.01-1 mM), verapamil (0.01-100 microM) and trifluoperazine (1-100 microM) were effective antagonists of CaCl2-induced responses. 2 Zn2+ and Cd2+ in concentrations from 0.01 to 1 mM were without effect on the tone of taenia and trachea in normal Tris solution. Conversely, Zn2+ and Cd2+, in concentrations of 1 mM, caused contraction of these tissues in a K+-rich, Ca2+-free medium. Zn2+ (1 mM)-induced contractions of taenia and trachea were completely inhibited by verapamil (10 microM). 3 In taenia and trachea sk…
Effects of alkylxanthines on contractility of diaphragm fibres isolated from normal and sensitized guinea-pigs.
1993
Abstract This study investigates the effects of alkylxanthines on twitch tension generated by electrical stimulation (supramaximal pulses, 0·2 ms duration, 1 Hz) of diaphragm muscle fibres isolated from normal and actively-sensitized guinea-pigs. Caffeine, theophylline and theobromine increased, in a concentration-dependent manner (50–500 μm), twitch tension in normal and sensitized diaphragm. Caffeine (500 μm) enhanced contractility to a greater extent than theophylline or theobromine. Twitch potentiation by caffeine (500 μm) was significantly greater in sensitized diaphragm. Verapamil (0·1–100 μm) did not alter twitch contractions in the absence or presence of alkylxanthines in normal or …
Differentiation of calcium antagonists with respect to their effects in normal and skinned taenia caeci preparations
1987
Abstract In taenia preparations, depolarized by a K+-rich medium, Ca2+ caused contraction and cinnarizine (0.4–100 μM), trifluoperazine (2–100 μM) and verapamil (0.02–10 μM) caused concentration-dependent antagonism of Ca2+, displacing the Ca2+ log concentration-effect curve to the right and depressing the maximal response. Equieffective (IC75) antispasmogenic concentrations were selected. The antispasmogenic effects of verapamil were readily offset by removing the drug from the bathing fluid but those of the other drugs were not. The calcium antagonists (antispasmogenic IC75) were then tested for spasmolytic activity in tissues generating tension in response to the EC80 of Ca2+. Verapamil …
Effect of verapamil and diltiazem on isolated gastro-oesophageal sphincter of the rat
1985
Abstract The effect of verapamil and diltiazem on the contraction induced by agonists on the rat lower oesophageal sphincter in-vitro has been studied. Both calcium entry blockers inhibited the contractile response to acetylcholine, carbachol and KCl. The potency of the inhibitory action was diltiazem > verapamil. The results give substance to the use of calcium entry blockers in the treatment of oesophageal spasm.
Effects of Ca2+ channel antagonists in guinea-pig normal and skinned gall bladder.
1993
CaCl2 (0.01-50 mM, in K(+)-depolarized tissues), KCl (0.1-100 mM) and acetylcholine (1 nM-10 mM) produced concentration-dependent contractions of guinea-pig isolated gall bladder. Nifedipine (1-100 microM), verapamil (1-100 microM), diltiazem (1-100 microM), cinnarizine (1-100 microM), and flunarizine (1-100 microM) each produced a concentration-related inhibition of the log concentration-effect curve for CaCl2. The rank order of potencies of these antagonists, measured as the IC50 against Ca2+ (50 mM)-induced contraction of depolarized gall bladder, was diltiazem (0.25 microM)or = verapamil (0.8 microM) approximately nifedipine (1.2 microM)cinnarizine (25 microM) approximately flunarizine …
Calcium dependence of the contraction produced by endothelin (ET-1) in isolated guinea-pig trachea.
1990
Endothelin (ET-1, 1 pM to 0.1 microM) produced a concentration-dependent contraction of isolated guinea-pig trachea. BAY K 8644 (1 microM) did not significantly alter the concentration-response curve for ET-1. Incubation with nicardipine (10 microM) partly inhibited responses to low concentrations (10 pM to 1 nM) of ET-1 while verapamil (10 microM) and diltiazem (10 microM) were ineffective. La3+ (10 microM) and Cd2+ (10 microM) preferentially depressed the responses evoked by high concentrations (30 nM-0.1 microM) of ET-1 without affecting the responses evoked by low concentrations of the peptide. Incubation in Ca2(+)-free (with EDTA, 1 mM) medium resulted in suppression of the responses e…
The influence of active secretion processes on intestinal absorption of salbutamol in the rat.
2001
Abstract Salbutamol was perfused in the small intestine of rat using a standard rat gut ‘in situ’ preparation: (1) in inhibitor-free solution at seven different concentrations (0.15, 0.29, 1.20, 5.0, 9.0, 13.0 and 18.0 mM); (2) at a 0.29 mM concentration – thought to be close to the allometric dose in man – in the presence of a non-specific enzyme inhibitor, sodium azide (0.3, 3.0 and 6.0 mM); and (3) at 0.29 mM in the presence of a selective secretion inhibitor, verapamil (10.0 and 20.0 mM). In free solution, the mixed-order rate constants, k ′ a , of salbutamol increase as the solute concentration increases until an apparent asymptotic value is reached. This could be due to the saturation…
Effects of calcium channel blockers on gastric emptying and acid secretion of the rat in vivo.
1986
Abstract Experiments were designed to evaluate the effects of three calcium channel blockers (verapamil, diltiazem and cinnarizine) on gastric emptying and secretion in the rat. Pretreatment with the calcium blockers delayed gastric emptying of phenol red in a dose-dependent manner. Verapamil was the most effective of the agents tested. Verapamil and diltiazem inhibited gastric acid secretion in the pylorus-ligated rat without affecting pepsin output. Cinnarizine was ineffective in this model. When the perfused lumen of the anaesthetized rat was used, verapamil was found to inhibit responses to carbachol or histamine more than those to pentagastrin. Further, we found a greater sensitivity t…
Differential Effects of Verapamil on Various Gastric Lesions in Rats
1988
Verapamil (3, 10, 20 mg/kg-1) increases the necrotizing effects of oral 25% NaCl or 100% ethanol. Damage by 0.6 N HCl was not equally affected since 1 mg/kg-1 of verapamil decreased the ulcer index whereas the higher doses augmented it. Pharmacologically induced gastric lesions were also differently affected by verapamil, ulcers produced by histamine being greatly enhanced and those of reserpine inhibited. Neither indomethacin nor compound 48/80 ulcers were modified. These results suggest that verapamil modifies the susceptibility of the gastric mucosa to damage.
Effects of low temperature and pharmacological interventions on the responses of the isolated guinea-pig trachea
1992
Cooling the guinea-pig isolated trachea from 37°C to 20°C virtually abolished the response to CaCl2 (in K+-depolarized tissues) and depressed that to histamine (about 75% reduction), KCl and 5-hydroxytryptamine (around 50% inhibition) while the response to acetylcholine remained unaffected. A further cooling to 10°C was necessary to inhibit acetylcholine-induced contractions. Hyporesponsiveness to spasmogens by cooling was not associated with subsensitivity (increased EC50) except for 5-hydroxytryptamine. Contractile responses to KCl (50 mmol/l), histamine (1 mmol/l) and 5-hydroxytryptamine (0.1 mmol/l) in a Ca2+-free EGTA (0.1 mmol/l)-containing solution were inhibited by cooling to 20°C b…