Effects of four calcium channel blockers on central cardiovascular control.

The cardiovascular effects of intravenous and intracisternal administration of low doses of calcium channel blockers (nicardipine: 0.3 to 10 micrograms/kg; nifedipine: 0.01 to 10 micrograms/kg; verapamil: 0.

Rilmenidine (S 3341) and the sympathoadrenal system: adrenoreceptors, plasma and adrenal catecholamines in dogs.

1. The effects of rilmenidine, a new alpha 2-adrenoreceptor agonist with antihypertensive properties, were investigated on plasma catecholamines, blood cell adrenoreceptors and adrenal medullary function. 2.

Involvement of cholinergic mechanisms in the central cardiovascular actions of nicardipine in dogs.

The involvement of cholinergic mechanisms in the central cardiovascular effects of a dihydropyridine, nicardipine, was investigated in pentobarbital-anaesthetized normotensive dogs. Nicardipine (1 microgram/kg) injected intracisternally (i.c.

A study of the action of clonidine on secretion from the adrenal medulla in dogs.

The effects of clonidine on adrenal catecholamine (adrenaline and noradrenaline) secretion were investigated in chloralose-anaesthetized dogs. Intravenous administration of clonidine (10 and 20 micrograms kg-1) induced a decrease in both adrenal catecholamine secretion rates and cardiovascular parameters (blood pressure and heart rate). In contrast, a dose of 5 micrograms kg-1 was ineffective.

Effects of calcium entry blockers on blood pressure and heart rate in neurogenic hypertensive dogs.

The hypotensive and negative chronotropic effects of 5 calcium entry blockers (verapamil 200 micrograms/kg IV; diltiazem 300 micrograms/kg IV; nifedipine 5 micrograms/kg IV; nicardipine 50 micrograms/kg IV; and bepridil 5 mg/kg IV) were compared in control normotensive and acute neurogenic hypertensive anaesthetized dogs. Acute neurogenic hypertension was induced by sino-aortic denervation (SAD). In control normotensive dogs, all drugs (except bepridil) induced a slight and transient decrease in blood pressure.

Antihypertensive effects of mesulergine: further evidence for a peripheral site of action of dopamine agonists.

The cardiovascular effects of mesulergine were studied in anesthetized dogs. Intravenous (IV) administration (0.3 mg/kg) significantly decreased blood pressure in neurogenic hypertensive dogs without any change in heart rate.

Naloxone reverses the effects of enalapril and enalaprilic acid on the pressor responses to afferent vagal stimulation.

The effects of intracisternal injection of enalapril (MK 421) or its bioactive form enalaprilic acid (MK 422) (0.075 mg/kg) on the pressor responses elicited by afferent stimulation of the vagus were investigated in the urethane-anaesthetized dog. The angiotensin converting enzyme inhibitors (ACEI)-induced decrease in the systolo-diastolic pressor responses to vagal stimulation was reversed by naloxone (0.

Reduction of vagal pressor reflexes by neurohypophyseal peptides and related compounds.

The effects of intracisternal injections of [Lys8]vasopressin and [Arg8]vasopressin (25, 50, 100, 200 mU/kg) and related compounds oxytocin (25, 50, 100, 200 mU/kg), felypressin (25, 50, 100, 200 mU/kg) and vasotocin (100, 200, 400, 800 ng/kg) on the acute neurogenic pressor responses to afferent vagal stimulation (5, 10, 20 and 30 Hz) were studied in urethane-anaesthetized dogs. [Arg8]vasopressin and [Lys8]vasopressin (50, 100, 200 mU/kg) elicited a significant decrease in the pressor responses. The depressor effects of oxytocin (50, 100, 200 mU/kg) were less marked and felypressin or vasotocin remained inactive.

The role of adrenal medulla and neurohypophysis in the central and peripheral cardiovascular effects of neurohypophysial peptides.

The cardiovascular effects of intravenous and intracisternal administration of neurohypophysial peptides were compared in normal, diabetes insipidus and adrenal demedullated chloralose anaesthetized dogs. In normal dogs, intravenous lysine vasopressin (0.1 to 100 mU/kg) induced a dose-dependent increase in blood pressure with bradycardia whereas intracisternal injection (0.

Neurohypophysial peptides and central cardiovascular control.

The cardiovascular effects of intravenous and intracisternal administration of neurohypophysial peptides were studied in anaesthetized dogs. Intracisternal oxytocin (1 and 10 mU kg-1) increased blood pressure. Intravenous lysine vasopressin (0.

Alpha-2 adrenergic antilipolytic effect in dog fat cells: incidence of obesity and adipose tissue localization.

The main intention of this study was to characterize the alpha-adrenoceptor responsible for the inhibition of lipolysis in dog fat cell and to define circumstances that may be associated to a modification of the alpha-mediated antilipolytic effect. Isolated fat cells from omental and subcutaneous adipose tissue from normal and obese dogs were used. Basal and theophylline stimulated lipolysis was studied in the presence of selected alpha-adrenergic agonists and antagonists.

Clonidine inhibits diuresis caused by negative pressure breathing and left atrial distension: role of central adrenergic alpha 2 receptors.

1. Intravenous (10 micrograms/kg) or intracisternal (1 microgram/kg) clonidine inhibited the diuretic response elicited by negative pressure breathing (NPB) or left atrial distension (LAD) in chloralose anaesthetized dogs. The drug reduced the induced tachycardia, but not the increase in respiratory rate elicited by NPB.

Clonidine-induced lipolysis in dog adipocytes by stimulation of histamine (H2)-receptors.

The effect of the alpha-adrenergic agonist clonidine on lipolysis was investigated in omental dog fat cells. In presence of theophylline, clonidine markedly enhanced lipolysis. This effect was competitively inhibited by the (H2)-receptor blocking agent cimetidine while the H1-histamine receptor antagonist (mepyramine) was without any significant effect.

Influence of hypocaloric diet on alpha-adrenergic responsiveness of obese human subcutaneous adipocytes.

Spontaneous and stimulated lipolytic activity of subcutaneous abdominal adipocytes from obese subjects treated by a hypocaloric diet (800-1000 kcal/d) for 13-15 d were studied. A strong increase in basal lipolytic activity of the adipocytes occurred after the restrictive diet treatment. Linked to this phenomenon, an important alpha-adrenergic antilipolytic effect of adrenaline appeared whereas, the beta-stimulating effect of isoproterenol (beta-adrenomimetic drug) was not affected.

[Adrenergic lipolysis in human fat cells: properties and physiological role of alpha-adrenergic receptors (author's transl)].

Lipolytic activity of human isolated fat cells from different fat deposits was studied. The purpose of the present investigations was to determine the epinephrine responsiveness, with regard to alpha- and beta-adrenergic receptor site activity, of omental and subcutaneous adipocytes (abdominal or from the lateral part of the thigh). Adipocytes were obtained from normal subjects or from obese subjects on iso- or hypocaloric diets.

[The role of beta and alpha adrenergic receptors in the lipolytic effect of catecholamines on dog adipocytes (author's transl)].

Pharmacological properties of adrenergic receptors have been investigated in fat cells isolated from omental adipose tissue of the Dog. From the results, the following points can be stated. 1.

[Reduction of adrenaline-dependent lipolysis in the adipose tissue of adrenalectomized dogs by an alpha adrenergic effect].

In dog, surrenalectomy reduces isoprenalino-depending lipolysis but still more adrenalino-depending lipolysis. Phentolamine potentializes the response to adrenaline but does not that observed with isoprenaline. Surrenalectomy unmasks an alpha adrenergical effect of adrenaline on adipocytes of dog adipose tissue.