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Biomedical subjects

C Brefel-Courbon

Publications and source records attributed to C Brefel-Courbon.

28 records · Page 2Linked to original sources
PubMed1998

Pressor and bradycardic effects of tacrine and other acetylcholinesterase inhibitors in the rat.

The cardiovascular effects of three different acetylcholinesterase inhibitors: physostigmine, tacrine and rivastigmine injected by intravenous (i.v.) route were compared in freely moving Wistar rats. The three drugs significantly increased both systolic and diastolic blood pressure and decreased heart rate. Compared to physostigmine, a 20-fold higher dose of tacrine and a 40-fold higher dose of rivastigmine was necessary to induce a comparable pressor effect. Tacrine was chosen as a model to study the mechanisms underlying the cardiovascular effects of i.v. cholinesterase inhibitors. Atropine totally abolished while methylatropine did not affect tacrine pressor effects. Conversely, both drugs abolished tacrine-induced bradycardia. The alpha1-adrenoceptor antagonist prazosin or the vasopressin V1 receptor antagonist, [beta-mercapto-beta,beta-cyclopenta-methylenepropionyl1, O-Me-Tyr2, Arg8] vasopressin partially but significantly reduced tacrine pressor effect and mostly abolished it when administered concomitantly. The tacrine pressor response was inhibited in a dose-dependent manner by the i.c.v. administration of the non-selective muscarinic receptor antagonist atropine (ID50 = 1.45 microg), the muscarinic M1 receptor antagonist pirenzepine (ID50 = 4.33 microg), the muscarinic M2 receptor antagonist methoctramine (ID50 = 1.39 microg) and the muscarinic M3 receptor antagonist para-fluoro-hexahydro-sila-difenidol (ID50 = 31.19 microg). Central injection of such muscarinic receptor antagonists did not affect tacrine-induced bradycardia. Our results show that acetylcholinesterase inhibitors induce significant cardiovascular effects with a pressor response mediated mainly by the stimulation of central muscarinic M2 receptors inducing a secondary increase in sympathetic outflow and vasopressin release. Conversely, acetylcholinesterase inhibitor-induced bradycardia appears to be mediated by peripheral muscarinic mechanisms.

Adrenergic Antagonists↗
PubMed1998

Central cardiovascular effects of tacrine in the conscious dog: a role for catecholamines and vasopressin release.

Centrally acting cholinergic agents are currently reported to increase blood pressure in various species through the stimulation of muscarinic cholinoceptors. Moreover, several cardiovascular adverse effects have been reported from clinical studies. The aim of this study was to investigate the effects of tacrine, an acetylcholinesterase inhibitor which has been reported to have therapeutic potential in Alzheimer's disease, on blood pressure and two vasopressor systems (sympathetic and vasopressinergic) in Beagle dogs. Intravenous (i.v.) tacrine (2 mg kg(-1)) induced, in conscious and anesthetized dogs, an increase in systolic and diastolic blood pressure, accompanied by bradycardia. This increase was dose-dependent with a peak effect at 1.5 min following administration. Tacrine also induced an increase in noradrenaline, adrenaline and vasopressin plasma levels. Pretreatment with the muscarinic receptor antagonist, atropine (2 mg kg(-1), i.v.), abolished the pressor response to i.v. injection of tacrine while pretreatment with the peripheral muscarinic receptor antagonist, methylscopolamine (0.2 mg kg(-1), i.v.), did not alter the increase in blood pressure. Similarly, noradrenaline and adrenaline changes in plasma levels were not modified by methylscopolamine but were abolished by atropine pretreatment. A similar tendency although not significant was observed for vasopressin plasma levels. The present results demonstrate that in dogs, tacrine (2 mg kg(-1), i.v.) stimulates central muscarinic cholinoceptors to increase blood pressure through activation of the two components of the sympathetic nervous system (i.e., neuroneuronal noradrenergic and the neurohormonal adrenergic pathways) as well as through increasing noradrenaline, adrenaline and vasopressin plasma levels.

Animals↗
PubMed1998

Efaroxan, an alpha-2 antagonist, in the treatment of progressive supranuclear palsy.

We have tested, in a prospective randomized, double-blind, placebo-controlled, crossover, 12-week study, the effects of 2 mg efaroxan, a potent alpha-2 antagonist, given three times per day to 14 patients with progressive supranuclear palsy. Efaroxan did not induce any significant change on any motor assessment criteria. The present data do not confirm the assumption that the blockade of alpha-2 receptors might be a useful pharmacologic strategy to improve patients with progressive supranuclear palsy.

Adrenergic alpha-Antagonists↗
PubMed1998

Fluoxetine in orthostatic hypotension of Parkinson's disease: a clinical and experimental pilot study.

Recent clinical studies have reported a beneficial effect of fluoxetine, a serotonin reuptake inhibitor, in patients with severe refractory orthostatic hypotension. The present study was undertaken to investigate the effect of fluoxetine in orthostatic hypotension occurring during Parkinson's disease on both blood pressure values and number of clinical symptoms during orthostatic procedure evaluated using a validated clinical rating scale. In a pilot study performed in fourteen patients with idiopathic Parkinson's disease plus orthostatic hypotension, fluoxetine hydrochloride (20 mg orally daily during one month) significantly reduced the fall in systolic blood pressure [-33 +/- 21 (SD) mmHg before fluoxetine vs -22 +/- 19 mmHg after fluoxetine, P = 0.03] elicited by standing without modifying heart rate. The drug also significantly reduced the number of postural symptoms occurring during the orthostatic procedure [2.9 +/- 1.5 (SD) before fluoxetine vs 1.2 +/- 1.3 after fluoxetine, P = 0.006]. A similar pattern of response was obtained in an experimental model of neurogenic orthostatic hypotension obtained in chronically sino-aortic denervated dogs submitted to an 80 degrees head-up tilt test procedure under chloralose anaesthesia. Fluoxetine did not change plasma noradrenaline levels. This pilot study suggests a slight but clinically significant effect of fluoxetine on both hemodynamic parameters and clinical symptoms in parkinsonian patients suffering from orthostatic hypotension.

Aged↗
PubMed1997

[Parkinson "plus"].

"Parkinson plus" is a group of sporadic degenerative disorders associating Parkinsonism, poorly sensitive to L-dopa, to other neurological syndromes. Thus, progressive supranuclear palsy includes Parkinson's disease, vertical gaze paralysis, nuchal dystonia and dementia; multisystem atrophies associate to different degrees Parkinson's disease (striatonigral degeneration), a cerebellar syndrome (olivopontocerebellar atrophy), dysautonomia (Shy-Drager syndrome), pyramidal syndrome, etc. Other diseases (corticobasal degeneration, diffuse Lewy body disease) also belong to the Parkinson "plus" group. Clinical differentiation between Parkinson "plus" and idiopathic Parkinson's disease is difficult. Their prognosis and treatment are substantially different. Certain diagnosis is based solely upon anatomical observations.

Antiparkinson Agents↗
PubMedDate not supplied

A pharmacoeconomic evaluation of botulinum toxin in the treatment of spasmodic torticollis.

We performed a prospective study in 21 patients to evaluate the cost of treatment of spasmodic torticollis (cervical dystonia) before and after botulinum toxin type A (BTA) treatment and to assess the impact of BTA treatment on quality of life. Data were recorded for the analysis over a period starting 8 months before and ending 7.2 +/- 0.2 months (mean +/- SEM) after the first injection of BTA. All patients received at least two BTA injections (2.9 +/- 0.2 injections per patient). We studied direct medical costs (drugs, outpatient and inpatient visits, diagnostic procedures, physiotherapy), clinical effects of BTA (clinical rating scale and patient's global assessment), quality of life (French version of the Nottingham Health Profile [NHP]), and adverse reactions. Costs associated with the treatment of spasmodic torticollis before the first BTA injection were 479 +/- 143 French Francs (FF)/patient/month (97 +/- 29 US $/pt/mo). During BTA treatment, costs were 1,126 +/- 147 FF/pt/mo (228 +/- 30 US $/pt/mo), including a mean cost of BTA of 771 +/- 131 FF/pt/mo (157 +/- 27 US $/pt/mo). Treatment with BTA significantly decreased clinical symptoms of spasmodic torticollis and improved the emotional, social, and pain-related domains of the quality of life assessment. Botulinum toxin type A treatment increases the cost of treating spasmodic torticollis but improves quality of life in terms of pain, social, and psychologic functioning in patients with spasmodic torticollis.

Adult↗
PubMedDate not supplied

Sleep attacks and antiparkinsonian drugs: a pilot prospective pharmacoepidemiologic study.

A prospective survey was performed to characterize the prevalence of sleep attacks and to evaluate precipitating factors in a group of 236 patients with idiopathic Parkinson's disease. Sleep attacks were reported by 72 patients (30.5%). Multivariate analysis showed a marked association between the occurrence of sudden sleep episodes and first autonomic failure, followed by treatment with ropinirole and bromocriptine. The present work underlines the major contributing role of autonomic failure followed by dopamine agonists in the occurrence of such an event. Because a relationship between sleep attacks and not only ropinirole but also bromocriptine treatment was described, the present work suggests that sleep attacks are a common side effect of all dopamine agonists.

Aged↗
PubMedDate not supplied

Fluoxetine-induced pressor response in freely moving rats: a role for vasopressin and sympathetic tone.

The present study was performed in order to assess, in freely moving rats, the cardiovascular effects of central administration of fluoxetine, a serotonin reuptake inhibitor. Two kinds of experiments were performed: 1) acute central administration of fluoxetine. and 2) chronic intraperitoneal administration of fluoxetine plus selegiline, a monoamine oxidase B inhibitor. Intracerebroventricular (i.c.v.) administration of fluoxetine (5-50 microg) induced an increase in blood pressure. This fluoxetine-induced pressor response reached its maximal 1 hour after injection without any significant change in heart rate. At the dose of 10 microg i.c.v., fluoxetine significantly increased mean blood pressure by 16 +/- 4 mmHg. This pressor response was reduced by an intravenous (i.v.) pretreatment with the alpha1-adrenoceptor antagonist, prazosin (500 microg kg(-1)) (+ 7 +/- 4 mmHg, P <0.05) or with the V1A-vasopressin receptor antagonist (20 microg kg(-1)) (+5 +/- 3 mmHg, P < 0.05). The pressor response was completely abolished by a concomitant pretreatment with prazosin plus the V1A-vasopressin receptor antagonist. Pretreatment with the beta-adrenoceptor antagonist, propranolol (1 mg kg(-1) i.v.), or the 5-HT2 receptor antagonist, ketanserine (5 mg kg(-1) i.v.), did not modify the fluoxetine-induced pressor response. In freely moving rats receiving fluoxetine (10 microg i.c.v.), vasopressin plasma levels were significantly higher (39 +/- 5 pg mL(-1) than in rats receiving 10 microL i.c.v. saline (14 +/- 4 pg mL(-1)). A 30 day intraperitoneal (i.p.) administration of fluoxetine in association with selegiline induced an increase in noradrenaline plasma levels and locomotor activity without any significant change in blood pressure and heart rate. These data suggest that, the pressor response elicited by central acute administration of fluoxetine is mediated by both an increase in sympathetic tone and vasopressin release. This observation could suggest the putative interest of alpha1-adrenoceptor and or V1A-vasopressin receptor antagonists in the treatment of "Serotonin Syndrome".

Analysis of Variance↗
PubMedDate not supplied

[Clinical pharmacology of dyskinesias induced by L-dopa in Parkinsonian patients].

Dyskinesias induced by L-dopa are involuntary and abnormal movements which lead to disablement and are observed in a lot of patients after some years of treatment. No drug has proved its efficacy for this indication. The use of D2 dopaminergic agonists as first treatment can delay their onset, delaying the need for L-dopa. New dopaminergic drugs, either with longer elimination half life or with specificity for subtypes of dopamine receptors may allow these dyskinesias to be managed more efficaciously. New non-dopaminergic, serotoninergic, adrenergic, opiate or gluamate drugs could offer antidyskinesia properties. The study of Parkinson disease's model in the methyl phenyltetrahydropyridine (MPT)-treated primate and the improvement in clinical evaluation of these dyskinesias could lead, in the short or medium term, to the discovery of new pharmarcological strategies, dealing more efficaciously with this serious adverse effect of L-dopa treatment.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗