Search results for "Smooth"
showing 10 items of 710 documents
Analysis of Rabbit Vascular Responses to DBI, an Ingol Derivative Isolated from Euphorbia canariensis
1997
Abstract We have analysed the effects of 7,12-O-diacetyl-8-O-benzoil-2,3-diepiingol (DBI), an ingol derivative isolated from E. canariensis, on isometric tension developed by isolated rabbit basilar and carotid arteries. Concentration-response curves to DBI (10−8 - 3 × 10−5 m) were obtained cumulatively in both arteries at resting tension and active tone (KC1, 50 mm). At resting tension, DBI induced a concentration-dependent contraction, which was not inhibited in Ca2+-free medium. H7 (1-(5-isoquinoline sulphonyl)-2-methylpiperazine dichloride) (10−4 m) inhibited the DBI-induced contraction both in basilar and in carotid arteries. Calmidazolium (10−4 m) inhibited the maximum contraction of …
Effects of inhibitors of cGMP-dependent protein kinase in atrial heart and aortic smooth muscle from rats
1995
Several activators of cGMP-dependent protein kinase (protein kinase G) such as 8-Br-cGMP reduced force of contraction in rat left atria. Inhibitors of protein kinase G antagonized the negative inotropic effect of 8-Br-cGMP but not of acetylcholine in atria. However, the acetylcholine-induced relaxation in aortic rings was significantly inhibited by protein kinase G inhibition. It is concluded that the reduction by 8-Br-cGMP of force of contraction in atria is related to activation of protein kinase G. In response to acetylcholine, activation of protein kinase G is probably a major step in smooth muscle relaxation but is not involved in the reduction of force of contraction in atria.
The Sources of Ca2+ for Muscarinic Receptor-induced Contraction in the Rat Ileum
1996
Abstract The contractile responses obtained by activation of different muscarinic receptor subtypes in the longitudinal muscle of the rat ileum and especially the responses of this muscle to acetylcholine in a Ca2+-free medium have been investigated. In Ca2+-containing solution, acetylcholine elicited similar concentration-dependent contractile responses in the duodenum, jejunum and ileum strips of the rat intestine. The response to a maximal concentration of the agonist (1 μM) consisted of a rapid phasic response followed by a slower tonic one. Nifedipine completely relaxes or inhibits the sustained response and only partially diminishes the phasic one, which suggests that the phasic contr…
Isolated human chorionic vascular reactivity: Technical considerations for fresh preparations
1998
1. 1. Sixty chorionic vascular rings from normal term placentas were immersed in an organ bath for isometric tension recording to study (A) the contractile response to 120 mM of potassium chloride (KCI) after adjustment and equilibration to 1–5 g of passive tension; and (B) the concentration-response curve to KCI after adjustment and equilibration to the optimal passive tension. 2. 2. Adjustment to 4 g of passive tension elicited the maximal (P<0.007) and the latest (P<0.006) KCl-induced contraction among arterial rings. Venous rings showed the greatest contraction when adjusted to 3 g, but the differences were not significant except when compared to 1 g of passive tension (P<0.03). 3. 3. T…
Effects of nicotine receptor agonists on acetylcholine release from the isolated motor nerve, small intestine and trachea of rats and guinea-pigs
1992
The effects of nicotine receptor agonists on the release of [3H]acetylcholine from the phrenic nerve, the small intestine and the trachea were investigated to characterize neuronal nicotine receptors within the peripheral nervous system. Contraction of the indirectly-stimulated hemidiaphragm was recorded to investigate desensitization of the postsynaptic muscular nicotine receptors. Nicotine, cytisine, 1,1-dimethyl-4-phenylpiperazinium and 2-(4-aminophenyl)-ethyl-trimethyl-ammoniumiodide caused a concentration-dependent (0.1-30 microM) increase in evoked [3H]acetylcholine release from the phrenic nerve, whereby bell-shaped concentration-response curves were obtained. The rank order of decre…
Antihistaminic and anticholinergic activities of mequitazine in comparison with clemizole
1988
Abstract The antihistamine and anticholinergic properties of mequitazine have been investigated and compared with those of clemizole. Both mequitazine and clemizole antagonized the effect of histamine in guinea-pig ileum competitively, the pA2 values calculated by Schild plot were 9.95 ± 0.44 for mequitazine and 10.54 ± 0.44 for clemizole. Mequitazine at 10−7 M produced a parallel shift of the dose-response curve to acetylcholine in the rat duodenum, clemizole and the lower doses of mequitazine failed to modify the effect of acetylcholine. The potency of mequitazine and clemizole as H1-histamine blockers is similar, but only mequitazine at highest concentration used showed anticholinergic a…
Effects of endothelin-1 on the cerebrovascular bed of the goat.
1991
Abstract The aim of the present study was to analyze the effects of endothelin-1 (ET-1) in the cerebrovascular bed of the goat, the importance of endothelial integrity and the contribution of extracellular Ca2+ to these responses. We measured isometric tension and 45Ca2+ uptake in isolated middle cerebral arteries, and cerebral blood flow (CBF) in unanesthetized animals. ET-1 elicited concentration-dependent contractions which were potentiated in arteries without endothelium. Ca2+-free medium and nicardipine inhibited, and Bay K 8644 potentiated the ET-1-induced contractions. ET-1 enhanced 45Ca2+ uptake in isolated arteries. Injections of ET-1 directly into the cerebral circulation decrease…
Isoflavones and cardiovascular disease
2010
The specific profile of estrogens on cardiovascular risk, with limiting action on atherogenesis but a less clear protection on cardiovascular episodes, might be improved by other agonists of the estrogen receptor, such as isoflavones. By using a systematic search based on the electronic Medline database plus a hand-search of reference lists of selected review papers, we reviewed the rapidly growing body of experimental and clinical data that, on average, follow a pattern of benefit rather similar to estrogens. Experimental models have used endothelial and vascular smooth muscle cells, isolated arteries, and live animals, including monkeys. The clinical evidence arises from studies on the li…
Functional relevance of presynaptic muscarinic autoreceptors.
1993
Pre- and postsynaptic muscarinic receptors have been characterized in the isolated trachea and ileal circular muscle of the guinea pig. The muscarinic autoreceptors mediating inhibition of acetylcholine release in the circular muscle belong to the M1 subtype, whereas those inhibiting acetylcholine release in the trachea are M2 or M4 receptors. In both tissues the postsynaptic muscarinic receptors are M3 receptors. Blockade of the autoreceptors by selective M1 and M2/M4 receptor antagonists leads to facilitation of cholinergic neurotransmission.
gamma-Aminobutyric acid and cholinergic transmission in the guinea-pig ileum.
1983
1. The effects of GABA on release of acetylcholine and on contractility of the smooth muscle were studied in the myenteric plexus-longitudinal muscle preparation of the guinea pig. Acetylcholine was determined as radiolabelled transmitter from strips preloaded with 3H-choline. 2. GABA (1–300 μM) caused an increase in resting tension of smooth muscle as well as an increase in release of acetylcholine that was considerably reduced by tetrodotoxin. The facilitation by GABA of acetylcholine release exhibited a marked tachyphylaxis. The increase in muscle tension was clearly related to the increase in acetylcholine release. Muscimol (0.1–10 μM) also enhanced the release of acetylcholine. The eff…