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At least 811 records · Page 45Linked to original sources
PubMed1979

[Sympathetic mediation of induced and spontaneous activity of the pelvis-ureter in vitro].

The spontaneous activity of guinea-pig renal pelvis-ureter is regulated by the adrenergic system. Spontaneous rhythmic contractions, and contractions induced by Noradrenaline are inhibited by Dihidroergotamine and Phentolamine. Alpha-adrenergic blocking agents block also contractions induced by histamine, angiotensin and barium chloride, but not contractions induced by electric stimulation. The Authors suggest an hypothetical model for the activation of the adrenergic receptor: Noradrenaline (NE) recognition sites are activated only by NE, whereas complementary sites can be activated by NE or other agonists. Both sites are blocked by alpha-adrenergic blocking agents.

Adrenergic alpha-Antagonists↗
PubMed1978

Prilocaine - barium chloride antagonism in the cardiovascular system of anesthetized dogs.

The intravenous administration of BaCl2 (2 mg/kg) in dogs anesthetized with nembutal determined sharp rise of arterial blood pressure, bradycardia, enlargement of PR interval and QRS complex, and bigeminated ventricular extrasystoles. Prilocaine (20 mg/kg iv) caused only slight fall of arterial blood pressure, mild bradycardia, enlargement of PR interval and QRS complex. When the drugs were administered simultaneously, prilocaine effectively antagonized pressor and heart rhythm alterations induced by barium. However, bradycardia and PR interval enlargement were even more severe, thus indicating a synergistic action of the drugs. It is shown that the statistical analysis based on a multiple regression model is quite suitable for this kind of experimental design.

Animals↗
PubMed1981

Castration atrophy and pharmacological reactivity of the rat coagulating gland.

1. The reactivity and sensitivity of the rat coagulating gland to acetylcholine, adrenaline, serotonin and barium chloride was studied 7, 15 and 30 days after castration. 2. The wet and the dry weight of the coagulating gland progressively decreased with time after castration. 3. Spontaneous contractions were observed in the coagulating gland 15 and 30 days after castration. 4. The maximum force developed per gram tissue was significantly higher than control for serotonin and barium chloride on the 7th day, while for acetylcholine and adrenaline the increase was observed only on the 15th day after castration. 5. The pD2 values for adrenaline, barium chloride and serotonin increased significantly 15 days after castration, whereas the change in sensitivity to acetylcholine was detected only 30 days after castration. 6. These results suggest that changes in reactivity and sensitivity of the rat coagulating gland caused by castration are not related only to muscle atrophy, since the time course of the development of the effects is different for the four agonists studied.

Acetylcholine↗
PubMed1981

Pharmacological responses by different portions of guinea pig vas deferens circular muscle preparation.

The different segments of the guinea pig vas deferens circular muscle exhibit differential response patterns upon pharmacological stimulation. Namely, apart from barium chloride, the affinity and intrinsic activity of certain agonists and the strength of maximum contractions they induce appear to decrease along the path from the epididymis toward the prostate. If one subdivides the vas deferens into 3 parts of equal length such as epididymal, medial and prostatic portions, then adrenaline, acetylcholine, acetyl-beta-methylcholine, dopamine, histamine and bradykinin induce contractions on each of the 3 parts; whereas tyramine, ephedrine elicit responses in the epididymal and medial portions; amphetamine, DMPP, serotonin and PGF2 alpha in turn provoking contractions exclusively on the epididymal portion. The effects of adrenaline and noradrenaline are blocked by phentolamine and tolazoline; the responses to acetylcholine, acetyl-beta-methylcholine and carbamyl-beta-methylcholine are antagonized by atropine over a specific concentration range. The effects of tyramine, ephedrine and amphetamine are inhibited by phentolamine in an remarkably low dose range (pA2 = 13.51 +/- 0.09; 14.54 +/- 0.31; 14.35 +/- 0.12). The situation was the same when tyramine-dibenamine and tyramine-phenoxybenzamine combinations were tested (pD'2 = 14.03 +/- 0.37; 13.26 +/- 0.03). Based on these findings the presence of a peculiar alpha adrenergic receptor is suggested on the sympathetic postganglionic fibres. In addition to the already identified alpha adrenergic, muscarinic cholinergic and histamine H1 receptors, we could show the presence of dopaminergic receptors too in the vas deferens circular muscle.

Acetylcholine↗
PubMed1984

[Different behavior of the rat vas deferens of castrated animals and those treated with cyproterone acetate].

The effects of castration and treatment with the antiandrogen cyproterone acetate (CPA) on the responses of the vas deferens of the rat induced by phenylephrine, KCl and BaCl2 has been studied. Both castration and CPA induced a spontaneous motility in the rat vas deferens. Castration produces a decrease of the response amplitude induced by phenylephrine and KCl and an increase of those induced by BaCl2 in animals killed 30 days after castration. CPA increases the response amplitude induced by phenylephrine and KCl without modifying those induced by BaCl2. These results suggest that the antiandrogen CPA produces modifications qualitatively different from castration.

Animals↗
PubMed1982

Antiarrhythmic effects of cyclic guanosine 3' :5'-monophosphate and sodium nitroprusside on barium chloride arrhythmias in rabbits.

The hypothesis that c GMP and sodium nitroprusside (NP), an activator of guanylate cyclase which elevates levels of c GMP, have antiarrhythmic activity was tested in the barium chloride (BaCl2) model of arrhythmias. Electrocardiograms were recorded continuously on tape in unanesthetized New Zealand white rabbits weighing approximately 2.0 kg. BaCl2, 4 mg/kg i.v. bolus, induced frequent ventricular ectopic beats. These ventricular arrhythmias were abolished by 8-bromo-c GMP, 5 mg/kg, injected into the left ventricle (5/6 rabbits), NP 25.0 microgram/kg/min i.v. (6/6), NP 10 micrograms/kg/min i.v. (3/6), and markedly reduced in frequency by NP 10 micrograms/kg/min (3/6). In temporal association with NP, 4 fold increases in c GMP levels in blood and significant increases in myocardial GMP were found compared to control animals (n = 6). In this model, c GMP and NP have significant antiarrhythmic properties. NP effect may be mediated by alterations in c GMP metabolism.

Animals↗
PubMed1983

Further studies on the effects of ketotifen on guinea pig ileum.

Ketotifen (Ke) at the concentration of 10(-5) M or greater significantly inhibits guinea pig ileum contractions induced by cumulative dose response curves to Pg alpha F2 or BaCl2. This inhibitory effect of Ke is also observable against ileal contractions induced by isotonic and hypertonic solutions with high K+ and by electrical stimulation. In contrast to the long term antihistaminic effect of DSCG and Ke, the latter drug exhibits a shorter inhibitory effect when Ach and electrical stimulation are used to induce ileal contractions shortly after Ke is removed by washing from the organ bath. This nonspecific protective effect of Ke on smooth muscle against various spasmogens resembles the one reported recently by us for DSCG and might be relevant to the antiallergic and antiasthmatic properties of both drugs.

Acetylcholine↗
PubMedDate not supplied

Effects of disodium cromoglycate (DSCG) on the guinea pig trachea and ileum.

Disodium cromoglycate (DSCG) (10(-2)M) significantly inhibits contractions induced by potassium chloride and barium chloride on guinea pig ileum and trachea. The effects of DSCG against these spasmogens are greater on the guinea pig ileum than on its trachea, which may be related with the calcium ion if we take into account that the contraction of the latter preparation seems to be less dependent on the extracellular calcium concentration than the first one. DSCG (10(-2)M) inhibits contractions induced by electrical stimulation (0.1 Hz) but the action of exogenous acetylcholine is not affected. This effect supports a neural site of action for DSCG in the ileum. DSCG (10(-2)M) also suppresses contractions induced by electrical stimulation (20 Hz) on isolated guinea pig trachea. This effect of DSCG is concentration and time dependent. The fact that DSCG inhibits contractions induced by electrical stimulation in both, guinea pig ileum and trachea as well as atropine does, constitute evidence that either an inhibition of acetylcholine release from postganglionic parasympathetic fibers or an anticholinergic effect is involved in the mode of action of DSCG. These effects can be ascribed to membrane stabilizing properties of this antiallergic drug.

Animals↗
PubMed1984

Influence of arrhythmogenic and antiarrhythmic agents on alternating current-induced arrhythmias in guinea-pig heart preparations.

The method for inducing arrhythmias or asystole by the application of a 50 Hz alternating current (ac) has been applied to isolated guinea-pig left atria and papillary muscles in order to characterize arrhythmogenic and antiarrhythmic substances. Aconitine, BaCl2 (less than 2 mmol/l) and hypoxia decrease threshold of ac-arrhythmia and ac-asystole, in both tissues to a similar extent, whereas carbachol and BaCl2 (greater than 2 mmol/l) increase threshold. The calcium antagonists nifedipine and diltiazem lower threshold of ac-asystole but differ with respect to threshold of ac-arrhythmia, which is increased by 10(-6) mol/l diltiazem in left atria and papillary muscles by about 30% and remains nearly unaffected with nifedipine. The Na+-inhibitory substance flecainide reverses the decrease in threshold of ac-arrhythmia and ac-asystole brought about by aconitine. Threshold of ac-arrhythmia lowered by hypoxia is increased by diltiazem in a concentration-dependent manner, whereas decrease of threshold of ac-asystole is even augmented. Therefore, the method offers an opportunity of quantifying the action of arrhythmogenic agents at concentrations which are too low to induce arrhythmia, as well as to characterize the activity of antiarrhythmic drugs in the presence of arrhythmogenic substances.

Aconitine↗
PubMed1984

Acute poisoning by a barium chloride burn.

A 62-year-old man sustained a barium chloride burn after his jackhammer penetrated a pocket of molten barium chloride. He subsequently developed signs of systemic barium poisoning including bigeminy and hypokalemia. Treatment consisted of early thorough debridement and intravenous potassium supplementation. Serum barium levels were determined. In a review of the literature these appeared to be the first toxic barium levels to be reported. The literature concerning barium poisoning and its complications is reviewed and related to the clinical presentation and treatment of this chemically burned patient.

Arrhythmias, Cardiac↗