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The lack of influence of some neuropeptides present in the posterior pituitary lobe on the frequency of spontaneous contraction of the isolated heart auricle

100%
Goraca A., Traczyk W. Z.
Acta Physiologica Polonica
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1990
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tom 41
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nr 7
Gorąca A., Traczyk W. Z.: The lack of influence of some neuropeptides present in the posterior pituitary lobe on the frequncy of spontaneous contraction of the sisolated heart auricle. Acta Physiol. Pol. 1940, 4 (6): Investigations have shown the presence of a cardiodepressant factor in the fluid incubating the posterior pituitary lobe “in situ”, which decreased contraction frequency of the isolated heart auricle (Acta Physiol. Pol., 1984, 35: 460-468). The influence on the spontaneuos contraction frequency of the isolated heart auricle of the following synthetic neuropeptides was determined: substance P, leu-enkephalin, met-enke- phalin, angiotensin II, arg-vasopressin, oxytocin, delta sleep-inducing peptide and atrial natriuretic factor. It was found that the investigated neuropeptides had no effect on the contraction frequency of the isolated auricle of the heart right atrium of two-day-old rat in a concentration from 2.1 × 10⁻⁷ to 1 × 10⁻³ mol/1 in the bathing medium and it was concluded that their biological properties differ from the cardiodepressant factor.
2
Content available remote

The role of Ca2plus in the contractility of rabbit small intestine in vitro

100%
Grasa L., Rebollar E., Arruebo M. P., Plaza M. A., Murillo M. D.
Journal of Physiology and Pharmacology
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2004
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tom 55
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nr 3
This study evaluated the role of Ca2+ in spontaneous and ACh- and KCl-induced contractions in longitudinal and circular smooth muscle from rabbit small intestine in vitro. In the first experiment, the amplitude, frequency and tone of spontaneous contractions in longitudinal and circular smooth muscle of small intestine were determined and, in the second experiment, the ACh- and KCl-induced responses of longitudinal and circular smooth muscle were measured. Atropine and guanethidine reduced the amplitude and tone of contractions in longitudinal and circular muscle, but reduced the frequency of contractions in circular muscle, only. TTX attenuated the amplitude of contractions and decreased the tone of contractions in longitudinal muscle, but increased the tone in circular muscle. Ca2+-free solutions, verapamil, nifedipine and caffeine diminished the three parameters of spontaneous contractions. Thapsigargin and cyclopiazonic acid increased the amplitude and tone of contractions in ileum longitudinal muscle, only, and cyclopiazonic acid increased the amplitude of contractions in circular muscle. Ca2+-free solutions, verapamil, nifedipine, thapsigargin, cyclopiazonic acid, and caffeine diminished ACh- and KCl-induced contractions. Those results suggest that extracellular Ca2+ plays a role in spontaneous contractions, and extracellular and intracellular Ca2+ participate in the ACh- and KCl-induced contractions of rabbit small intestine.
3
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The role of NO in the contractility of rabbit small intestine in vitro: effect of K+ channels

80%
Grasa L., Rebollar E., Arruebo M. P., Plaza M. A., Murillo M. D.
Journal of Physiology and Pharmacology
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2005
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tom 56
|
nr 3
Nitric oxide (NO) is an inhibitory neurotransmitter of intestinal smooth muscle cells. The aim of this study was to determine the role of NO in the contractility of rabbit small intestine smooth muscle in vitro. The amplitude, frequency and tone of spontaneous contractions in longitudinal and circular smooth muscle of duodenum, jejunum and ileum were determined and the sodium nitroprusside (SNP), acetylcholine (ACh) and KCl responses were quantified. L-NAME, L-NNA, L-arginine and D-arginine did not affect the amplitude, frequency and tone of spontaneous contractions. ODQ (10-6 M) increased the tone of spontaneous contractions of the types of tissues examined, and the amplitude in ileum, without modifying the frequency. SNP (10-4 M) evoked relaxations that were not influenced by atropine (10-6 M) plus guanethidine (10-6 M), apamin (10-8 M) or glybenclamide (10-6 M), but were increased by TTX (10-6 M) and verapamil (10-7 M). SNP-induced relaxations were reduced by charybdotoxin (10-8 M) and ODQ (10-6 M). ODQ (10-5 M) reduced ACh-induced contractions, but it did not influence KCl-evoked contractions. Those results suggest that NO modulates the spontaneous contractions of small intestine in rabbits. This effect is mediated by cGMP and Ca2+-dependent K+ channels of large conductance.
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