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Biomedical subjects

A Courtière

Publications and source records attributed to A Courtière.

13 recordsLinked to original sources
PubMed2004

Short-term vasomotor adjustments to post immersion dehydration are hindered by natriuretic peptides.

Many studies have described the physiology of water immersion (WI), whereas few have focused on post WI physiology, which faces the global water loss of the large WI diuresis. Therefore, we compared hemodynamics and vasomotor tone in 10 trained supine divers before and after two 6h sessions in dry (DY) and head out WI environments. During each exposure (DY and WI) two exercise periods (each one hour 75W ergometer cycling) started after the 3rd and 5th hours. Weight losses were significant (-2.24 +/- 0.13 kg and -2.38 +/- 0.19 kg, after DY and WI, respectively), but not different between the two conditions. Plasma volume was reduced at the end of the two conditions (-9.7 +/- 1.6% and -14.7 +/- 1.6%, respectively; p < 0.05). This post-WI decrease was deeper than post DY (p < 0.05). Cardiac output (CO) and mean arterial blood pressure were maintained after the two exposures. Plasma levels of noradrenaline, antidiuretic hormone and ANP were twofold higher after WI than after DY (p < 0.05). After DY total peripheral resistances (TPR) were increased (p < 0.05) and heart rate (HR) was reduced (p < 0.05). After WI there was a trend for a decrease in stroke volume (p = 0.07) with unchanged TPR and HR, despite more sizeable increases in plasma noradrenaline and vasopressin than after DY. We hypothesized that the higher levels of plasma natriuretic peptides after WI were likely counteracting the dehydration-required vasomotor adjustments.

Adult↗
PubMed2003

Selective effects of low-dose dopamine D1 and D2 receptor antagonists on rat information processing.

It is well established that the dopaminergic system influences simple reaction time (RT) performance. However, the role of this system in more complex information processing remains to be clarified. The present study was aimed at addressing this issue. To this end, we used an inferential method that relies on choice RT procedures and allows one to identify information processing stages in both humans and rats. Long-Evans rats responded to lateral visual cues (left or right). Two task factors, signal intensity and foreperiod duration, were manipulated. Low doses of two pharmacological agents, SCH 23390 (a D1 receptor antagonist; 0.015 and 0.025 micromol/kg) and eticlopride (a D2 receptor antagonist; 0.01 and 0.02 micromol/kg), were administrated systemically. Both drugs increased choice RT: eticlopride interacted with signal intensity on RT, showing that D2 receptors mediate at least the sensory stage of stimulus preprocessing. In addition, eticlopride interacted with signal intensity on omission rate, thereby suggesting an involvement of D2 receptors in attentional processes; and SCH 23390 interacted with foreperiod duration on RT, indicating that D1 receptors specifically mediate the response adjustment stage. The effect of this drug on RT rests entirely in its interaction with foreperiod duration, allowing us to conclude that this D1 antagonist affects the response adjustment stage while sparing all other processing stages.

Animals↗
PubMed2000

The additive factor method in rat information processing.

Sternberg introduced the additive factor method as a tool for discovering and studying in choice reaction time situations in human subjects. Underlying the method is the notion that if information processing consists of successive stages, then different factors affecting different stages must have additive effects on reaction-time measurements. The additive factor method has been extensively used in humans but few attempts have been made to examine whether or not additive reaction time patterns were obtainable in rats. In the present work, the subjects (13 Long-Evans rats) had to press down a lever and to respond to a visual (right or left) stimulus by releasing the lever and introducing the head into a lateral (right or left) operandum. The present findings show an additive pattern of effects of signal luminance and foreperiod duration on the mean reaction time which suggests that we have successfully manipulated two stages of rat information processing - the preprocessing stage and the motor adjustment stage, respectively. Accordingly, the present study sets the basis for the basis for investigating the effects of invasive manipulations (pharmacological and/or lesional) on information processing stages.

Journal Article↗
PubMed1997

Behavioural effects induced by nitrous oxide in rats performing a vigilance task.

Nitrous oxide (N2O) effects were evaluated, as a behavioural model of inert gas narcosis, in rats performing a vigilance task in which they were required to respond to a slight luminous increment of the house-light. A dose-related decrease of correct responses was produced by the tested range of concentrations of N2O (from 30 to 70% N2O), with a parallel increase of anticipatory responses up to 60% N2O and a dramatic increase of omissions at 70% N2O. The influence of preparatory period duration on hits delays suggested a 'conditional probability effect' conserved under N2O. Pretreatment of animals with flumazenil (a central benzodiazepine receptor antagonist) did not improve performance under 40% N2O. Naltrexone, an opiate receptor antagonist, however, increased the N2O-induced deficits. These results suggest that benzodiazepine receptors are not involved in N2O-induced impairments in this attentional task, but opiate mechanisms may be implicated.

Animals↗
PubMed1985

Effects of the 1,5-benzodiazepine clobazam on pituitary hormones in the male rat.

The aim of this study is to evaluate the effects of the acute and subchronic administration of the benzodiazepine clobazam (20 mg/kg orally) on the plasma levels of the pituitary hormones (prolactin, FSH and LH) in the male rat. This 1.5 benzodiazepine did not induce any variation of the hormone levels either after acute or subchronic administration. These negative data are discussed as compared to the effects of other benzodiazepines of GABA and GABA receptor agonists and antagonists on the pituitary hormone levels according to particular experimental conditions.

Animals↗
PubMed1983

Immunoreactive Cu-SOD and Mn-SOD in lymphocytes sub-populations from normal and trisomy 21 subjects according to age.

Copper and manganese superoxide dismutases (Cu-SOD and Mn-SOD) were measured by radioimmunoassay in B and T lymphocytes and macrophages, in patients with trisomy 21 and in matched controls. In the controls, Cu-SOD was present in greater amounts than Mn-SOD and there were quantitative differences in the distribution in the three cellular sub-populations. In trisomy 21, levels of Cu-SOD were raised, with no change in levels of Mn-SOD, supporting the theory of a gene dosage effect. There were significant positive and negative correlations between age and Cu-SOD levels in controls, and a correlation approaching significance for Mn-SOD. In trisomy 21, there was no correlation between age and Cu-SOD levels, and the only significant correlation for Mn-SOD was for B lymphocytes.

Adolescent↗
PubMed1982

[Neuro-endocrine effects of chronic clonidine administration in rats].

Neuroendocrine effects of chronic clonidine administration - which has been proposed as antimanic drug - have been evaluated in the female rat for a twenty one days period at the following doses : 0,5 ; 5 ; 25 and 50 micrograms.kg-1.day-1. No modification of the evolution of the oestrus cycle was observed, whereas pituitary hormones (PRL, FSH and LH) plasma levels were not statistically modified. The results of this study are opposed to those frequently observed with classical neuroleptic drugs.

Animals↗
PubMedDate not supplied

[Lipid peroxidation in aged patients. Influence of an antioxidant combination (vitamin C-vitamin E-rutin)].

Lipoperoxidation has an important role in the normal processes of the cell-life. The induction is produced by oxygen-derived free radicals which attack the membrane phospholipids. Such an attack is modulated by an enzymatic protection system (superoxide dismutase, catalase, glutathione peroxidase, glutathione transferase) and by a non-enzymatic one (vitamin C, vitamin E...). In various pathologic conditions, a dispoise takes place between radical attack and antiradical protection. The place taken by lipoperoxidation in the ageing process seems to be fundamental. We report here the results of a study carried out in aged and sick patients who were given an antioxidant medicamentous combination made from Vitamin C, Vitamin E and Rutin. Our results evidence that such a synergistic combination does modify both enzymatic protection system and lipoperoxidation, this latter showing a decrease under treatment.

Aged↗
PubMedDate not supplied

[Neuroendocrine effects of the chronic administration of carbamazepine in male and female rats].

Relationships between epilepsy, antiepileptic drugs and neuroendocrinological events justify the study of an eventual influence of antiepileptic drugs of the regulation mechanisms of ovulation. Thus carbamazepine effects on the oestrus cycle of female rats and on FSH, LH and PRL serum levels has been studied. Carbamazepine was given orally once daily for 21 consecutive days to Wistar AF SPF female (exhibiting regular 4 days cycles) and male rats: three doses were used: 100, 10 and 5 mg per kg bodyweight. Oestrous cycle was studied by daily vaginal smears. Our data show that carbamazepine do not significantly modify the evolution of oestrous cycle nor FSH, LH or PRL serum levels. These results agree with those of literature even if literature data have been obtained with a single administration in man. Finally our data confirm also a previous work on oestrous cycle effects of perinatal exposure to carbamazepine in the female rat.

Animals↗
PubMedDate not supplied

[Neuroendocrine effects of a sodium valproate and diazepam combination in the male rat].

The effects of chronic administration of sodium valproate (200 mg/Kg/d i.p.) and diazepam (5 mg/Kg/d i.m.) alone or in association on the plasma levels of the pituitary hormones (prolactin, FSH and LH) were studied in the m ale rat. Sodium valproate increases prolactin plasma levels. This effect is antagonized by diazepam. Both molecules do not affect FSH levels, whereas they increase LH levels when given alone or in association. This pharmacological data state precisely the hypothalamohypophysiotropic effects of valproate and diazepam during its association.

Animals↗