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Biomedical subjects

O D Gulati

Publications and source records attributed to O D Gulati.

At least 19 recordsLinked to original sources
PubMed2001

Influence of chronic treatment of rats with isoprenaline and calcium channel blockers on response of isolated right ventricle to noradrenaline.

Influence of chronic treatment of rats with and calcium channel blockers (CCBs) and isoprenaline (ISP) on responses to noradrenaline (NA) was investigated on electrically--driven isolated right ventricle preparations. The ventricles were obtained from animals treated with chronic ISP or CCBs alone and chronic nifedipine, verapamil, diltiazem or nimodipine plus chronic ISP. A decreased response to NA as evidenced by an increase in EC50 for contraction which was observed in chronic ISP- treated preparations may be due to development of desensitisation (down-regulation) of beta-adrenoceptors. In chronic CCB-treated preparations there was a significant decrease in the EC50 of NA and decreased contractile response suggesting an increase in the beta-adrenoceptors and decreased availability of calcium, respectively. In chronic CCBs + ISP treated preparations further decreases in the EC50 values were observed suggesting that the voltage gated L-type Ca2+ channels may be affected directly or indirectly by change in beta-adrenoceptor activity. By the above results a proposed mechanism of interrelationship of beta-adrenoceptors with voltage gated L-type calcium channels in cardiac muscle is supported.

Animals↗
PubMed1996

Interaction of calcium channel blockers with different agonists in aorta from normal and diseased rats.

The interactions of calcium channel blockers (CCBs) with noradrenaline (NA), phenylephrine (PE), dopamine (DA) and KCl have been investigated in rat isolated aortic strip. In preparations from control and hypertensive (DOCA-saline) rats chronically treated with verapamil, nifedipine and diltiazem, there was partial inhibition of contractions to NA, PE and DA. However, with nimodipine, there was potentiation of responses. This could be related to the occurrence of different isoforms of L-type calcium channels. In preparations obtained from hyperthyroid rats the concentration-response curves of NA, PE and KCl were shifted to the right with depressed maximal response which could be secondary to the primary effect exerted on the heart. In preparations from L-thyroxine + nimodipine/nifedipine treated rats the concentration-response curves of NA, PE and KCl were shifted to the right and the maxima was depressed suggesting that this may be due to decreased alpha receptor density (NA and PE) and down-regulation of voltage operated channels (KCl).

Adrenergic alpha-Agonists↗
PubMed1996

Interaction of calcium channel blockers (CCBs) with histamine and 5-hydroxytryptamine in aorta from normal and diseased rats.

The present study attempts to investigate the interaction of calcium channel blockers (CCBs) with histamine (H) and 5-hydroxytryptamine (5-HT) in rat isolated aortic strip preparations. In preparations obtained from rats chronically treated with various CCBs the contractile responses to H were completely blocked suggesting that this may be due to inhibition of the voltage-dependent channels and inositol 1,4,5-triphosphate induced release of calcium from intracellular stores. The decreased contractions of the aortic strip preparations with 5-HT obtained from rats chronically treated with various CCBs implies a decrease in 5-HT receptor density. DOCA-saline hypertensive rats chronically treated with various CCBs showed variable responses to H and 5-HT suggesting that these changes may be due to different isoforms of L-type calcium channels. In L-thyroxine-treated preparations or those simultaneously treated with L-thyroxine and CCBs the responses to H were abolished and those to 5-HT were partially blocked with decrease in maxima which could be secondary to the primary effect on the heart and to generalised reduced senstivity of the rat aorta.

Animals↗
PubMed1992

Evaluation of xanthotoxol for central nervous system activity.

Xanthotoxol (XT), 8-hydroxypsoralen, exhibited dose-graded sedative activity in dogs, cats, rats, mice and hamsters. At doses of 5-20 mg/kg intraperitoneally (i.p.) in cats and 3-100 mg/kg orally (p.o.) in dogs, XT blocked predatory mouse/rat killing behavior. In mice, XT (10-300 mg/kg i.p.) exhibited a dose-dependent reduction in locomotor activity but was less potent in this regard than reference diazepam (10-100 mg/kg i.p.). XT in mice (0.1-10.0 mg/kg i.p.) and in hamsters (0.1-10.0 mg/kg p.o.) antagonized amphetamine-induced hypermobility but was less potent than diazepam. XT elevated the electrical threshold in foot-shock-induced fighting behavior in rats. XT (0.1-30.0 mg/kg p.o.) potentiated pentobarbital-induced narcosis in hamsters at otherwise subeffective doses of pentobarbital. Conditioned avoidance responses in rats were not significantly altered with 1-3 mg/kg i.p. and 30-100 mg/kg p.o. doses of XT but 300 mg/kg p.o. blocked both conditioned and unconditioned response. Doses of 100-1000 mg/kg i.p. of XT in mice were used to study 48-h acute toxicity of XT and its LD50 was estimated to be 468 mg/kg. Doses of 10, 40 and 80 mg/kg p.o. were used to study the chronic toxicity of XT in rats for 6 months and no side effects or abnormalities in reproductive activity or endocrine integrity were noted. The F1 generation of rats from 6-month XT-treated parents were free of teratogenic effects.

Animals↗
PubMed1990

Effect of cadmium on contractile response to spasmogens in vascular and nonvascular tissues.

In rat isolated aorta low concentration of CdCl2 (4.8 x 10(-8) M) produced a significant increase in pD2 value of KCl and noradrenaline (NA) with an increase in the maxima, while higher concentration of CdCl2 (1.44 x 10(-5) M) produced a significant rightward shift of the dose-response curve with a depression of maxima. In rat isolated portal vein 4.8 x 10(-7) M CdCl2 produced a significant increase in the pD2 value of KCl with an increase in the maxima, while higher concentration of CdCl2 (4.8 x 10(-5) M) produced a significant rightward shift of the dose-response curve of KCl and NA with a depression of maxima. In rat isolated vas deferens and anococcygeus muscle 4.8 x 10(-8) M CdCl2 produced a significant increase in pD2 value of KCl with an increase in the maxima, while higher concentrations of CdCl2 (4.8 x 10(-6) M and 1.44 x 10(-5) M) produced a significant rightward shift of the dose-response curve of KCl and NA. It is suggested that enhancement and reduction of response to KCl and NA, in presence of different concentrations of CdCl2 might be due to the alteration in the fluxes of calcium ion since these spasmogens produce their action by increasing the availability of calcium ions for the contractile machinery.

Animals↗
PubMed1989

Cadmium-induced hypertension in rats.

Chronic cadmium chloride (CdCl2, 0.5 and 1.0 mg/kg, i.p.) treatment in female albino rats for 2 weeks resulted in elevation of blood pressure. In chronic CdCl2-treated rats the pressor responses to different doses of noradrenaline, angiotensin II and depressor responses to acetylcholine and isoprenaline were unaltered. In rat hindquarter preparation there was elevation of perfusion pressure and the sensitivity of vascular bed to noradrenaline was increased in the CdCl2-induced hypertensive rats. Complete bilateral adrenalectomy or chemical sympathectomy or treatment with captopril did not prevent the development of CdCl2-induced hypertension. Treatment with verapamil (15 mg/kg/day, p.o.) or nifedipine (10 mg/kg/day, p.o.) for 2 weeks prevented the development of hypertension with chronic CdCl2 treatment. It is suggested that chronic treatment of rats with CdCl2 induces hypertension. It is possible that cadmium mimics the calcium ion for the induction of hypertension in rats.

Acetylcholine↗
PubMed1988

Effects of Abana, an Ayurvedic preparation, on rabbit atrium and intestine.

The effects of Abana, an Ayurvedic remedy, administered orally to rabbits was studied for its effects on isolated atria and intestine. Administration of Abana for 3 days increased the basal amplitude and reduced the responses of atria to isoprenaline and norepinephrine. Combined treatment with Abana and isoprenaline reduced this effect. It is possible that Abana treatment for 3 days has an action similar to that of chronic administration of isoprenaline (down regulation of beta receptors). A similar down regulation of beta receptors of smooth muscle of rabbit intestine also seems to occur. Abana pretreatment potentiated the inotropic responses of histamine and CaCl2. These effects may be due to a specific depressant effect of Abana on the adrenergic receptors and a direct sensitization of the atrium manifested by an increased response to CaCl2.

Acetylcholine↗
PubMed1986

The role of the sympathetic nervous system in oestrogen-induced hypertension in rats.

Albino rats of either sex received chronic ethinyl oestradiol (EO) treatment (1.5 mg kg-1 daily, i.m.) for 3 weeks. Untreated control rats received arachis oil vehicle alone. Chronic EO treatment resulted in elevation of blood pressure in both sexes. Female rats exhibited significantly greater elevation in blood pressure than males. In chronic EO-treated rats pressor responses to low doses (0.5 micrograms kg-1) of noradrenaline were significantly increased, while those to angiotensin II, acetylcholine and isoprenaline were unaltered. Chronic EO treatment also sensitized the vascular bed of the rats' hindquarters to noradrenaline. EO-induced hypertension was associated with significant increase in dopamine-beta-hydroxylase activity of adrenal glands. Complete bilateral adrenalectomy or chemical sympathectomy prevented the development of EO-induced hypertension. It is suggested that chronic treatment of rats with EO induces and maintains hypertension. The peripheral sympathetic system plays an important role in this phenomenon.

Adrenalectomy↗
PubMed1985

Interactions of levamisole with some autonomic drugs on guinea-pig vas deferens.

The effects of levamisole on responses to various agonists were studied in guinea-pig vas deferens. Levamisole did not itself exhibit any contractile or relaxant effect on guinea-pig vas deferens but in the presence of levamisole the concentration-response curve of noradrenaline (NA) was shifted to the left and the maximal response was increased. Responses to field-stimulation at 5 and 10 Hz were potentiated by levamisole. Cocaine and denervation caused potentiation of NA responses and these enhanced responses remained unchanged in the presence of levamisole. Acetylcholine (ACh) responses were potentiated by levamisole whereas responses to histamine, KCl and methoxamine remained unaltered. These results suggest that levamisole does not have any action at postsynaptic alpha-adrenoreceptors. The increased responses to NA and ACh in the presence of levamisole may be due to its uptake1, blocking and anticholinesterase activities respectively.

Animals↗
PubMed1984

Investigation of the muscle relaxant activity of nitrazepam.

Administered intravenously in decerebrate cats nitrazepam or diazepam (0.0625 to 0.5 mg/kg) produced dose-related inhibition of the ipsilateral extensor reflex. Nitrazepam (0.25 mg/kg i.v.) produced a significantly greater (P less than 0.001) inhibition than that produced by diazepam (0.25 mg/kg i.v.). Nitrazepam or diazepam (0.0625-4 mg/kg i.v.) had no effect on the contractions of directly stimulated (120 V, 5 msec, 0.1 Hz) quadriceps femoris muscle and on the contractions of tibialis anterior muscle produced by stimulating the cut peripheral end of the lateral popliteal nerve (8 V, 1.5 msec, 0.1 Hz). Nitrazepam or diazepam (0.125-0.5 mg/kg i.v.) produced dose-related depressor responses in cats anaesthetized with chloralose or pentobarbitone. Nitrazepam produced a depressor response at 0.0625 mg/kg dose while diazepam did not. The drugs did not appear to have any deleterious effect on the veins removed 6 hr after the first exposure to the drugs as evidenced by lack of histological changes. It is concluded that nitrazepam and diazepam produce central muscle relaxation by inhibiting polysynaptic pathways in the spinal cord. The potency of nitrazepam appears to be greater than that of diazepam. Definitive evidence has been provided that the peripheral neuromuscular or direct muscular actions are not involved in the muscular relaxation produced by the two drugs.

Anesthesia↗
PubMed1983

influence of Mg++ and reserpine on the reactivity of rat seminal vesicle to 5-hydroxytryptamine.

The effects of varying the concentration of Mg++ in the incubation medium on the contractile responses of rat isolated seminal vesicle to 5-hydroxytryptamine (5-HT) were investigated in the absence and presence of EDTA. Preparations incubated in Mg++-free and Mg++ excess media showed supersensitivity and subsensitivity to 5-HT respectively. In the presence of EDTA alterations in the sensitivity to 5-HT produced by varying the concentrations of Mg++ were comparatively less. Preparations obtained from reserpinized animals showed subsensitivity in normal and Mg++ excess media and supersensitivity in Mg++-free medium. In the presence of EDTA, reserpinized preparations showed slight supersensitivity in normal Mg++ medium, marked supersensitivity in Mg++-free medium and lesser subsensitivity in Mg++ excess medium. Probably EDTA by more effectively removing Mg++ from the membrane binding sites by chelation makes the membrane permeable to Ca++ leading to supersensitivity to 5-HT (observed only in the presence of EDTA). These results suggest that the failure of reserpine to induce supersensitivity to 5-HT in rat seminal vesicle may be due to an enhanced antagonism of Mg++ on Ca++ movements in this preparation due to the poor capacity of rat tissue to retain Ca++ (Krishnamurty and Grollman, 1976).

Animals↗
PubMed1981

Blockade of 5-hydroxytryptamine-induced responses of rat seminal vesicle by lithium-possible mediation through calcium exchange..

Effect of lithium on the contractile responses of rat isolated seminal vesicle to 5-hydroxytryptamine (5-HT) were investigated by varying the Ca++ and Mg++ concentrations of the incubation medium in the absence and presence of EDTA. Preparations incubated in excess Ca++ (4.2 mM) or in Ca++-free Krebs solution showed decrease in sensitivity to 5-HT, whereas the responses to 5-HT were potentiated in Mg++-free incubation media and reduced in media containing excess Mg++. Rezerpinization failed to induce supersensitivity to 5-HT in any Mg++ concentration in the medium. However, reserpinized tissue in Mg++-free solution with EDTA showed increased sensitivity to 5-HT. Li+ inhibited responses to 5-HT. The inhibitory action of Li+ was augmented in medium lacking in Ca++ and was antagonized in media containing excess Ca++ (4.2mM). Li+ reduced the sensitivity and decreased maximum responses to 5-HT in any Mg++ concentration in the medium. In the presence of EDTA, the inhibition observed with Li+ in excess Mg++ (3.6 mM) medium was comparatively much less in both non-reserpinized and reserpinized preparations. Thus Li+ may be inhibiting responses to 5-Ht by block of influx of Ca++ or delayed efflux of Ca++ or inhibition of uptake of Ca++ or a combination of two or more of these effects.

Animals↗
PubMed1980

Influences of Mg++ and reserpine on calcium fluxes and sensitivity of the rat aorta.

Rat aorta became supersensitive and subsensitive to noradrenaline (NA), respectively, in Mg++-free and 3.6 mM Mg++ media reserpine treatment reduced the sensitivity in normal or high (3.6 mM) Mg++ media but had no effect in Mg++-free medium. Incubation of aortae in Mg++-free medium enchanced 45Ca++ uptake and efflux in rat aorta, whereas, it reduced 45Ca++ efflux without a change in 45Ca++ uptake by rabbit aorta. Reserpine pretreatment enhanced 45Ca++ efflux from rat aorta without a changed in 45Ca++ uptake in normal Mg++-free medium. Unlike in rat aorta, reserpine enhanced 45Ca++ uptake by and reduced efflux from rabbit aorta in Mg++-free medium but not in normal medium. These results suggest that the failure of reserpine to induce supersensitivity in rat aorta to NA may be due to poor capacity of the muscle to retain Ca++ and probably also due to an enhanced antagonism of Mg++ on Ca++ movements.

Animals↗
PubMed1979

Investigation of the mechanism of decreased sensitivity of the rat seminal vesicle to norepinephrine by lithium.

Li+ is reported to reduce sensitivity of alpha-adrenergic receptors to NE. The present investigation was designed to investigate the mechanism of this decreased sensitivity on the rat isolated seminal vesicle. In innervated preparations, 1.35 X 10(-3) M Li+ (i) shifted the concentration-response curves of NE, methoxamine, ACh and BaCl2 to the right and reduced their maximum responses; (ii) antagonized the leftward shift and the enhancement of maximum responses to NE by cocaine (2.9 X 10(-4) M), and (iii) reduced only the maximum responses to KCl. In denervated preparations, 1.35 X 10 (-3) M Li+ shifted the concentration response curve of NE to the left without any change in the maximum responses. The antagonistic effects of Li+ on maximal responses to NE, ACh and KCl observed in innervated preparations were significantly increased in Ca++-free medium. Li+ (1.35 X 10(-3) M) increased NE uptake by the seminal vesicle significantly. It is concluded that decreased sensitivity of the seminal vesicle to NE by Li+ could be due to an increase in the uptake of NE and to a nonspecific postsynaptic spasmolytic action.

Acetylcholine↗
PubMed1978

Some observations on the development of adrenergic innervation in rabbit intestine.

1 Stimulation of periarterial nerves to the ileum of 1 to 12 day old rabbits with supramaximal voltages and frequencies of 1, 2, 5, 10 and 20 Hz with square wave pulses of 2--5 ms duration for 30--40 s produced responses that were initially contractor. In the course of the first week, the responses changed from motor to inhibitory, the change occurring first at the highest rates of stimulation. By the 7th day of life, almost all responses were inhibitory. 2 The motor responses were potentiated by physostigmine and blocked by hyoscine suggesting that they were mediated by acetylcholine. 3 In preparations from rabbits older than 3 days, motor responses could be converted to inhibitory ones by prior exposure to noradrenaline (NA, 1 microgram/ml) for 20 min. This procedure also significantly increased the responses which were already inhibitory. 4 The ability of the ileum to take up NA increased with age. This uptake was blocked by cocaine. 5 The following explanations are possible: (a) changeover from cholinergic to adrenergic transmission in sympathetic fibres; (b) existence of 'parasympathetic' splanchnic nerves or a permanent cholinergic 'sympathetic' component of splanchnic nerves and (c) temporal delay in the development of adrenergic nerves (compared with cholinergic nerves) in the intestine.

Aging↗