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Mandal A K - - 1989
Urapidil is thought to lower blood pressure by both a peripheral and a central mechanism. The former effect is caused by blockade of alpha-1 adrenoceptors whereas the latter effect has been shown to occur in the medulla, specifically at the intermediate area on the ventral surface of the medulla. The ...
Munari L - - 1989
To characterize autonomic imbalance in migraine, we compared the cardiovascular reflex responses of 10 migraineurs and 10 healthy subjects after pharmacological noradrenergic stimulation or inhibition. A battery of 5 autonomic tests was administered on basal conditions as well as after pretreatment with drugs acting at different levels on the noradrenergic ...
Millan M J - - 1989
This study examined the comparative efficacy of mu- and kappa-opioids in modulating the tail-withdrawal response to matched intensity heat and pressure stimuli and the vocalization response to electrical stimulation in the rat. All drugs were given s.c. The mu-agonists, morphine and fentanyl, were equipotent against heat and pressure at all ...
Kooner J S - - 1989
1. To investigate the contribution of sedation to the cardiovascular effects induced by clonidine, we studied patients with essential hypertension on two separate occasions when similar levels of sedation were induced by clonidine and nitrazepam. 2. After clonidine, there was a fall in blood pressure, heart rate, digital skin vascular ...
Engelman E - - 1989
The authors studied in a double-blind placebo-controlled study the effects of oral preoperative administration of 5 micrograms/kg clonidine upon the alfentanil and droperidol requirements, hemodynamic lability, distribution of the values of heart rate and blood pressure, and plasma noradrenaline levels, in two groups of ten normotensive patients undergoing infrarenal aortic ...
McAuley M A - - 1989
1. The cardiovascular responses to neuropeptide-Y (NPY) (25 and 50 pmol) and clonidine (10 and 20 nmol) were examined following microinjection into the rostral ventrolateral medulla (RVLM) and the caudal ventrolateral medulla (CVLM). Mean arterial pressure (MAP) and heart rate (HR) were measured in anaesthetized rats, pre- and post-injection. 2. ...
Smallman K - - 1989
The purpose of this study was to investigate the effects, if any, of high pressure on opiate analgesia. The interaction of high pressure with intrathecal morphine (2.5-15 micrograms) and pethidine (10-145 micrograms) was studied on the responses of 51 dorsal horn neurones in the intact rat under urethane anaesthesia to ...
Gurtu S - - 1989
Intravenous veratrine induced alterations in cardiovascular parameters in cats were used as a tool for assessing the influence of central alpha-adrenoceptors over reflex adjustments in the heart rate and blood pressure. Blockade of central alpha 2-adrenoceptors with idazoxan or yohimbine, inhibited, while their activation by clonidine, as also blockade of ...
Siu P M - - 1989
The mechanism of action of PTIQ in lowering the arterial blood pressure in the anesthetized dog was studied using pharmacological and physiological techniques. The hypotensive activity of PTIQ was significantly inhibited by pretreatment with bilateral vagotomy, propranolol, prazosin and mecamylamine. Pretreatment with either yohimbine or reserpine had no significant effect ...
Kapoor V - - 1989
Blood pressure (BP), hypothalamic tissue concentrations and the in vivo overflow of endogenous and alpha-methylated catecholamines were measured in urethane anaesthetised rats after alpha-methylDOPA (mDOPA) administration (200 mg/kg i.p.). Four hours after mDOPA, BP fell to its lowest value, 60% of control, and slowly returned towards control levels by 24 ...
Schmieder R E - - 1989
Ambulatory blood pressure recordings and stress blood pressures during exercise were compared among hypertensive patients effectively treated with oxprenolol, nitrendipine, enalapril or low-dose clonidine. After 6 months of therapy, the means of blood pressure at rest and casual diastolic pressure were nearly identical among the four therapeutic groups. Although all ...
Fillingim J M - - 1989
Long-term antihypertensive treatment by once-weekly application of transdermal clonidine patches, in doses equivalent to 0.1, 0.2, 0.3 mg of clonidine daily, was evaluated in an open trial of 41 patients with baseline seated diastolic blood pressures of 90 to 103 mmHg. In all the patients, seated diastolic blood pressure was ...
Lund C - - 1989
The effect of lumbar epidural clonidine 150 micrograms on early (less than 0.5 s) somatosensory evoked potentials (SEP) to electrical stimulation of the L1 and S1 dermatomes was examined in twelve cancer patients. Epidural clonidine led to a minor but significant decrease in amplitude of two components (N1 and N3) ...
Hof R P - - 1989
1. 8-Hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT) and flesinoxan, agents which show high affinity and selectivity for 5-HT1A receptors, were administered intravenously in doses of 0.003 to 0.1 and 0.01 to 0.3 mg kg-1 respectively to 5 rabbits each. Their effects were compared with those of the centrally acting agent and alpha 2-adrenoceptor ...
Haniuda M - - 1989
By using the cannula inserting method, vasoconstrictor responses to norepinephrine (a mixed alpha-1 and alpha-2 adrenoceptor agonist), phenylephrine (a selective alpha-1 adrenoceptor agonist), clonidine and xylazine (selective alpha-2 adrenoceptor agonists) were investigated in the isolated and perfused canine pulmonary vein. The segment of vessels was perfused by Krebs-Ringer bicarbonate solution ...
Cheav S L - - 1989
Intravenous (i.v.) administration of penta-O-ethylquercetin (PQ) dissolved in glycerolformal (GF) induced a rapid and transient fall in arterial blood pressure of rats. The mechanism appears rather complex. Beside its inhibitory properties toward cardiac cyclic AMP phosphodiesterase, the drug seems to lower the adrenergic tone, thus acting both at the central ...
Fuglsang G - - 1989
The bronchodilator effect of three successive stable plasma terbutaline levels was studied in 10 children with asthma. Each terbutaline plateau was achieved by giving a rapid intravenous infusion of terbutaline, 0.9 microgram/kg, followed by a continuous infusion for 2 hours. Mean plasma terbutaline concentrations (18, 36, and 53 nmol/L at ...
Forster C - - 1989
The interactions between yohimbine (selective alpha 2-antagonist) with noradrenaline (mixed agonist) and phenylephrine (selective alpha 1-agonist) were studied in the canine dorsal pedal artery in an attempt to characterize the peripheral vascular response to adrenergic agents before and after the development of congestive heart failure in the dog. The contractile ...
Chang A P - - 1989
Intravenous injection of clonidine produces a biphasic blood pressure response, a transient increase followed by a prolonged decrease. Significant increases in plasma norepinephrine (NE), epinephrine (EPI), and dopamine (DA) levels occur 5 min following injection, corresponding to the hypertensive phase. Thirty minutes after clonidine injection, blood pressure, NE, EPI, and ...
Eisenach J C JC Department of Anesthesia, Wake Forest University, Bowman Gray School of Medicine, Winston-Salem, NC - - 1989
Administration of intravenous clonidine hydrochloride has been advocated to rapidly control blood pressure in severe preeclampsia. To examine clonidine's acute maternal and fetal effects were intravenously injected 300 micrograms clonidine in eight chronically prepared normotensive near term ewes. Unlike intravenous saline solution injection, clonidine produced significant toxicity--intraamniotic pressure increased 97 ...
de Mey C - - 1989
SK&F 86466 is a novel alpha-adrenoceptor blocking drug shown in preclinical profiling to have relative selectivity for the pre- and postjunctional alpha 2-adrenoreceptor. In the present clinical study, the effects of single oral doses of 10, 25, and 50 mg SK&F 86466 on supine and stimulated circulatory and neuroendocrine function ...
Mathias C J - - 1989
The efficiency and duration of action of a single oral dose (8 mg) of tizanidine in patients with spinal cord injuries were determined by studying its antispastic, cardiovascular and sedative effects along with its pharmacokinetic profile in five tetraplegic and five paraplegic patients. After the administration of tizanidine, there was ...
Eisenach J C JC Department of Anesthesia, Wake Forest University, Bowman Gray School of Medicine, Winston-Salem, North Carolina - - 1989
Epidural clonidine administration produces analgesia by a nonopiate, spinal mechanism, and offers advantages over other epidural agents for labor analgesia. To examine clonidine's acute maternal and fetal effects, the authors injected clonidine, 300 micrograms, epidurally in seven chronically prepared, near term ewes. Unlike epidural saline injection, clonidine increased maternal and ...
Widdop R E - - 1989
The present study reports the effects of 2-amino-6-allyl-5,6,7,8-tetrahydro-4H-thiazolo-[4,5-d]azepin dihydrochloride (B-HT 920) and 2-(2,6-diethylphenylimino)-2-imidazolidine hydrochloride (St 91) in autoperfused cat hindquarters since we have previously shown that clonidine lowered blood pressure, heart rate and vena cava blood flow (VCBF) but not hindquarters perfusion pressure, indicating a selective venodilator action of this ...
Neusy A J - - 1989
The effects of placebo, propranolol, and clonidine on blood pressure and blood pressure variability were examined in 14 subjects who had moderate essential hypertension. Hydrochlorothiazide was given throughout successive 4- to 5-week periods of placebo, propranolol, and clonidine administration. During each treatment period, subjects were admitted twice to the clinical ...
Reggiani P - - 1989
A middle-aged man was admitted to our department because of sleep-wake cycle disorders (alternating hypersomnia and sleeplessness), bipolar behavioural disturbances and marked fluctuations in blood pressure and heart rate. Neither evident precipitating stimuli nor an obvious cause for his illness were found. When tests that normally activate intrinsic autonomic responses ...
De Saedeleer V - - 1989
In 13 anaesthetized hens in the peak phase of their first laying year the influence of intravenously injected substance P (SP), 1-10 micrograms/animal, on oviductal pressure, duodenal pressure, blood pressure and heart rate has been studied within 5 h of oviposition. The neuropeptide induced a significant pressure increase in the ...
Pinto J M - - 1989
The interaction between opiate and adrenergic receptors on cardiac electrophysiologic function in the conscious dog was addressed in our study. We examined the effects of opiate receptor blockade with naloxone on clonidine-induced changes in refractoriness of the cardiac ventricle. Nine dogs were chronically instrumented for recording mean arterial blood pressure, ...
de Leonardis V - - 1989
Since high blood pressure might be more harmful the higher it is and the more it remains above a determined critical value (140/90 mm Hg - 18.7/12.0 k Pa - in the present study), the hyperbaric impact, a measure of the total load exerted on the arterial walls and the ...
Mylecharane E J - - 1989
Robustoxin, a polypeptide consisting of a chain of 42 amino acid residues in a known sequence, has been isolated by cation exchange chromatography from the crude venom of the male funnel-web spider (Atrax robustus). Physiological activity or toxicity in the venom fractions was detected by production of fasciculation in mouse ...
Rabkin S W - - 1989
The purpose of this study was to evaluate the effects of the millimicrons opioid agonist D-Ala-2-Me-Phe-4-Gly-ol enkephalin (DAGO) on catecholamine-induced arrhythmias. Arrhythmias were produced, in the rat, by continuous infusion of epinephrine until the development of fatal arrhythmias that were usually ventricular fibrillation. Intracerebroventricular (ICV) administration of DAGO, 3 nmol, ...
Yamaguchi N - - 1988
This study reports on the effects of yohimbine and clonidine on the release of adrenal and renal catecholamines (epinephrine, E; norepinephrine, NE; and dopamine, DA) in response to bilateral carotid occlusion (BCO, 3 min) in vagotomized dogs anesthetized with sodium pentobarbital. The model used allowed us to simultaneously compare adrenal ...
Petty M A - - 1988
1. The purpose of this study was to investigate the role of an intact baroreceptor reflex mechanism in the expression of the cardiovascular response to 8-OH-DPAT and to determine whether there are any differences between the activation of central alpha 2-adrenoreceptors and 5-HT1A receptors in this respect. To this end, ...
Kooner J S - - 1988
The role of central pressor mechanisms in the maintenance of blood pressure in six hypertensive patients with angiographically proven unilateral renal artery stenosis was investigated by studying the haemodynamic and hormonal responses before and after central sympathetic blockade with clonidine. To assess the dependency of blood pressure on the direct ...
Cullen L K - - 1988
Blood pressure and heart rate were recorded continuously in methoxyflurane anaesthetized dogs. Amitraz (i.v.) caused a dose-dependent rise in blood pressure with a fall in heart rate at lower doses. Pressor responses to amitraz were reduced by phentolamine and slightly enhanced by atropine and hexamethonium, while bradycardia was reduced by ...
Gulati A - - 1988
The effects of three kappa opioid agonists namely, bremazocine, tifluadom and U-50,488H were studied on blood pressure and heart rate in urethane-anesthetized normal and bilateral adrenal demedullated rats. Bremazocine (0.2, 0.4 and 0.6 mg/kg i.v.) produced a dose-dependent decrease in heart rate, while only 0.4 mg/kg bremazocine produced marked hypotension. ...
Dallman, Mary F.
The putative neurotransmitters, L-glutamate and norepinephrine were microinjected (50nl) unilaterally into the paraventricular nucleus of pentobarbital-anesthetized rats. L-glutamate (0.5M) elicited a rise in plasma ACTH, vasopressin, and oxytocin and a profound drop in heart rate that was accompanied by no significant change in blood pressure. The bradycardia was blocked by ...
Yamazaki R - - 1988
The alpha-adrenoceptor agonist ST-1059 (2-amino-1-(2,5-dimethoxyphenyl) ethanol), the alpha 1-adrenoceptor agonist methoxamine, the alpha 2-adrenoceptor agonist clonidine and a nonselective alpha-adrenoceptor agonist norepinephrine, all increase cardiac output and dose-dependently increase arterial blood pressure in spinally anesthetized ganglion-blocked dogs. The increase in cardiac output may be the result of an increased venous ...
Bhaskaran D - - 1988
The effect of drug-induced hypertension and hypotension on neurotransmitter metabolism in the locus coeruleus (LC) of urethane anesthetized rats was studied using in vivo electrochemical methods. Peaks were seen at +0.15 V and +0.28 V. Studies with alpha-methylparatyrosine, fusaric acid and pargyline showed the first peak was produced by extracellular ...
Batra Y K - - 1988
Forty healthy patients (ASA class 1) of both sexes, aged between 20 and 45 years, undergoing routine surgical procedures were included in this double-blind randomized study. They were divided into two groups of 20 each. Patients in group A received no pretreatment, while patients in group B received oral clonidine ...
Donnerer J - - 1988
1. The involvement of alpha 2-adrenoceptors in a capsaicin-induced depressor reflex in the rat has been investigated. 2. The reflex fall in blood pressure following an intra-arterial injection of capsaicin was partially blocked by an intrathecal infusion of clonidine (1 microgram) at the spinal cord level L4-L5, an effect which ...
May C N - - 1988
1. In conscious rabbits, intravenous morphine (3 mg/kg) caused hypertension, bradycardia, hyperglycaemia and sedation. These changes were accompanied by large increases in plasma adrenaline and smaller increases in plasma noradrenaline. 2. These effects of morphine were prevented by intravenous naloxone, demonstrating their dependence on stimulation of opiate receptors. 3. Pretreatment ...
Roden D M - - 1988
Clonidine can produce symptomatic sinus bradycardia or atrioventricular (AV) block in some patients. Electrophysiologic studies have been performed after intravenous clonidine in patients showing such side effects; these have demonstrated variable depression of sinus and AV nodal function. We have evaluated the electrophysiologic and hemodynamic effects of chronic oral treatment ...
Ghignone M - - 1988
The effects of clonidine on intraocular pressure and perioperative cardiovascular variables were studied by a randomized double blind design in 80 elderly patients (ASA physical status I-III) scheduled for elective ophthalmic surgery under general anesthesia (GA) and local anesthesia (LA). Group 1 (n = 40), the control group, received diazepam ...
Elliott H L - - 1988
A single-dose comparative evaluation in young normotensive men of the plasma concentrations and alpha-adrenoceptor antagonism after conventional prazosin and a new slow-release formulation (Oros) is described. Whereas conventional prazosin (2 mg) produced a maximum reduction in erect blood pressure at 3 hours (80/46 mm Hg compared with 110/65 mm Hg ...
Hamilton C A - - 1988
The effects of infusion of alpha-adrenoceptor agonists on blood pressure, pressor responses to bolus doses of agonists and to platelet aggregation were examined in rabbits with perinephritis hypertension and in sham-operated controls. Pressor responses to bolus doses and infusions of phenylephrine, an alpha 1-selective agonist, were greater in hypertensive rabbits. ...
Gatti P J - - 1988
The purpose of our study was to determine whether clonidine exerts its centrally mediated hypotensive action at three sites that influence arterial pressure located in the medulla, specifically associated with the intermediate area of the ventrolateral medulla. The "intermediate area" lies approximately 1.5 mm caudal to the border of the ...
Dire D J - - 1988
We report the case of a 46-year-old woman who took approximately 8 mg of clonidine in a suicidal gesture. She arrived in the emergency department 45 min after the overdose with severe hypertension and an altered mental status. Nitroprusside, which is the drug of choice for treating this "paradoxical hypertension," ...
Jarrott B - - 1988
Clonidine is a centrally acting antihypertensive drug that acts in vivo at both alpha 1- and alpha 2-adrenoceptor sites, whereas rilmenidine (S 3341) is more selective for alpha 2 adrenoceptors. The present study compared the effects of continuous 10-day infusions of clonidine (5 micrograms/kg/hour) with those of rilmenidine (100 micrograms/kg/hour) ...
Nutt D - - 1988
Central alpha-2-adrenoceptor function was studied in seven withdrawing alcoholics and compared with seven normal controls using the clonidine challenge test. The alcoholic group had significantly elevated basal levels of blood pressure and plasma 3-methoxy-4-hydroxy-phenyl glycol. The percentage of fall in blood pressure produced by clonidine was blunted in the alcoholics. ...
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