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R M Tripathi

Publications and source records attributed to R M Tripathi.

36 records · Page 2Linked to original sources
PubMed1986

A simple method for the production of ventricular tachycardia in the rat and guinea pig.

A simple method for the production of ventricular tachycardia in the rat and guinea pig was developed. The animals were made to inhale benzene vapors for 2 min. An intravenous injection of adrenaline was given during the last 30 sec of benzene administration. Ventricular tachycardia developed in 95% of the animals used. Development of ventricular tachycardia in guinea pigs was earlier than in rats, but the duration of the ventricular tachycardia was almost equal in both species of animals. The arrhythmia developed by this method is of short duration, reliable, and reproducible. This method can be utilized for the rapid screening of antiarrhythmic agents.

Animals↗
PubMed1986

Effects of alpha-adrenoceptor agonists and antagonists on ouabain-induced arrhythmias and cardiac arrest in guinea-pig.

Effects of alpha-adrenoceptor agonists and antagonists with different affinity for alpha 1- and alpha 2-receptors on ouabain-induced arrhythmias in guinea-pigs were studied. Early arrhythmias, ventricular fibrillation and cardiac arrest were induced in anaesthetized guinea-pigs by the slow intravenous infusion of ouabain. Phenylephrine and yohimbine potentiated the cardiotoxicity of ouabain significantly whereas prazosin and clonidine showed significant antiarrhythmic effects and delayed the cardiac arrest. It is concluded that selective alpha 1-receptor stimulation and alpha 2-receptor blockade increases the cardiotoxic effects of ouabain and selective alpha 2-receptor stimulation and alpha 1-receptor blockade inhibits ouabain-induced arrhythmias and cardiac arrest in guinea-pigs.

Adrenergic alpha-Agonists↗
PubMed1985

Polysorbate 80: a pharmacological study.

Polyoxyethylene (20) sorbitan monooleate (polysorbate 80, Tween 80), a surfactant, has been widely used as a solvent for pharmacological experiments. In the present study, polysorbate 80 was found to have toxicity of a low order in both the mice and rats when given by i.p. and p.o. routes. It produced mild to moderate depression of the central nervous system with a marked reduction in locomotor activity and rectal temperature, exhibited ataxia and paralytic activity and potentiated the pentobarbital sleeping time. On intravenous administration in dogs, it had a dose-dependent hypotensive effect. Polysorbate 80 did not have a direct stimulant or relaxant effect on either guinea pig ileum or rat uterus, however, it antagonised the contractions induced by acetylcholine, histamine, barium, 5-hydroxytryptamine and carbachol in a dose-dependent manner. A direct relaxant effect was observed on rabbit jejunum. A dose-dependent myocardial depressant effect was observed on guinea pig and rabbit paired atrial preparations. On the electrically-driven guinea pig left atrial preparation, polysorbate 80 exhibited a dose-dependent negative inotropic action. Polysorbate 80 did not induce diuresis in rats upto a dose of 2.5 ml/kg. The results of the present study indicate that polysorbate 80 can neither be used as a solvent for isolated tissue experiments nor when considered for intravenous administration. However, polysorbate 80 can be employed safely as a vehicle for neuropsychopharmacological experiments in doses not exceeding 1 ml/kg.

Animals↗
PubMed1982

A pharmacological study of propane-1,2-diol.

Propane-1,2-diol (propylene glycol, PG), considered to be a safe solvent and commonly used as a vehicle in pharmacological and toxicological investigations, showed various neuropsychopharmacological activity in albino mice and rats. In lower concentrations (10-20%), at dose level of 10 ml/kg, PG did not show any significant neuropsychopharmacological activity either by i.p. or p.o. routes. But higher concentrations (50-100%), at same dose level by i.p. route, were found to have moderate to marked effect. There was decrease in locomotor activity, body and limb tone, respiration, rectal temperature and suppression of secondary conditioned responses. Significant potentiation of pentobarbitone (pentobarbital) hypnosis, slight increase in d-amphetamine toxicity in aggregated mice and pronounced analgesic and anti-inflammatory activity were also observed. Most of the above effects were also observed on p.o. treatment but the effects were of lesser degree. PG did not produce any effect on dog or cat blood pressure up to 100% concentration at the dose level 0.5 ml/kg. However, it potentiated the adrenaline (epinephrine) and noradrenaline (norepinephrine) response. On isolated smooth muscle preparations, in 50-100% concentrations, a dose-dependent non-specific blockade was observed against agonists viz. acetylcholine, histamine, 5-HT and barium chloride. No effect was seen on cardiac tissue preparation. On the basis of present findings, it is suggested that propylene glycol as a solvent be used only in low concentration of not more than 10% for pharmacological and toxicological investigations.

Analgesics↗
PubMed1979

Studies on the mechanism of action of Albizzia lebbeck, an Indian indigenous drug used in the treatment of atopic allergy.

Studies were conducted on the decoction of the bark of Albizzia lebbeck which has been in use by Ayurvedic physicians for bronchial asthma and eczema. The effect of A. lebbeck was studied on the degranulation rate of sensitized peritoneal mast cells of albino rats when challenged with antigen (horse serum). Triple vaccine was used as adjuvant. Disodium cromoglycate (DCG) and prednisolone were used for comparison. Drugs were given during the first or second week of sensitization and the mast cells studied at the end of the second or third week. Serum from these rats was used to passively sensitize recipient rats whose peritoneal mast cells were then studied. The in vitro effects of A. lebbeck and DCG on the degranulation rate of the sensitized mast cells were also studied. The results show that A. lebbeck has a significant cromoglycate-like action on the mast cells. In addition, it appears that it inhibits the early processes of sensitization and synthesis of reaginic-type antibodies. If A. lebbeck is given during the first week of sensitization it markedly inhibits the early sensitizing processes, while if given during the second week it suppresses antibody production during the period of drug administration. The active ingredients of the bark appear to be heat-stable and water-soluble.

Adrenal Glands↗
PubMed1978

Studies on mast cells of Rana tigrina.

Mast cell degranulators cause vasoconstriction in the frog. A comparative study of the mesenteric mast cells of the frog and rat showed that the frog mast cells differed from those of the rat in having a dense perigastric instead of a sparse ideal distribution, and in responding to compound 48/80 by a rapid and marked disappearance and/or fragmented appearance instead of classical degranulation. The vasoconstriction and mast cell response after in vivo compound 48/80 appeared related since they showed a parallel increase when the dose was increased.

Animals↗
PubMedDate not supplied

Effect of various hypotensive agents on locomotor activity and blood pressure of rats.

The effect of various hypotensive agents were simultaneously tested on locomotor activity and blood pressure of unanaesthetised (conscious) rats. The agents viz clonidine, prazosin, furosemide and hexamethonium were found to reduce significantly the locomotor activity as well as blood pressure, 30 min post administration. Phenoxybenzamine and alpha-methyldopa produced similar type of effect but after 60 and 120 min post administration respectively. Aminophylline and propranolol failed to reduce locomotor activity as well as blood pressure, 60 and 90 min post administration. The findings of the present study are strongly indicative that hypotensive agents reduce locomotor activity and that the reduction is sequel to the fall in blood pressure.

Animals↗
PubMedDate not supplied

Solvent artifacts likely to be induced by dimethylformamide.

Dimethylformamide (DMF) is widely used as a drug solvent. We found DMF to have wide-spread pharmacological effects including depressant effect on CNS evidenced by a decrease in locomotor activity, body and limb tone and rectal temperature, and potentiation of pentobarbitone sleep. A dose-dependent hypotensive effect was seen in cats and rats. In rats, it was partially blocked by atropine and was associated with bradycardia. DMF antagonised the contractions of smooth muscle induced by many agonists. An atropine sensitive spasmogenic effect was observed on rabbit ileum at 20 ml/l and a direct relaxant effect at 50 ml/l. A positive inotropic effect on guinea pig atria was observed with 5 ml/l. The results indicate DMF concentrations that may not perhaps produce 'solvent artifacts' when used as a solvent.

Animals↗
PubMedDate not supplied

Protective effect of ST-93 against ouabain induced arrhythmias in guinea pigs.

ST-93, a clonidine analog was studied for its antiarrhythmic activity in anaesthetised guinea pigs against ouabain induced arrhythmia. The amount of ouabain required (micrograms/kg) for the production of ventricular premature best. Ventricular fibrillation and cardiac arrest was recorded in control and drug treated group of animals. Both ST-93 and clonidine produced significant antiarrhythmic effect in guinea pigs. This protective effect was significantly blocked by yohimbine, suggesting that the antiarrhythmic effect is mediated through presynaptic alpha 2-adrenoceptors.

Animals↗