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Biomedical subjects

G Chouvet

Publications and source records attributed to G Chouvet.

At least 55 records · Page 3Linked to original sources
PubMed1989

Continuous volume infusion improves circulatory stability in anesthesized rats.

'Optimized' management (OM) was provided to chloralose-anesthetized rats for 12 h by combining continuous infusion (7 ml.kg-1). mechanical ventilation and strict control of acid-base equilibrium (n = 7). The chloralose-anesthetized rats managed conventionally (conventional management: CM, n = 9) received neither volume infusion, nor mechanical ventilation, nor correction of acid-base disturbances. All the OM rats completed the study while 6 out of 9 CM rats died before the end of the study period. Mean arterial pressure (MAP) remained at 100 mmHg for 12 h in the OM group. MAP stayed close to 70 mmHg in the CM group for 6 h and declined to very low levels thereafter (mean +/- S.E.M.: 46.0 +/- 3.9 mmHg at 12 h, P less than 10(-4) when compared to the other group). Central venous pressure and cardiac output remained close to baseline values for 12 h in the OM group. Acid-base equilibrium was preserved in the OM group in contrast to a severe metabolic acidosis in the CM group (pH = 7.14 +/- 0.03 at 12 h; P less than 10(-4). Such as 'optimized' management involving mechanical ventilation with oxygen, continuous infusion and acid-base monitoring may be of value to maintain circulatory stability in anesthetized rodent preparations during long periods of time, as in neurophysiological experiments.

Anesthesia↗
PubMed1984

Brain diurnal levels of adenosine 3',5' cyclic monophosphate in C57 BL/6 and BALB/C mice.

Adenosine 3',5'-cyclic monophosphate (cAMP) was measured in whole brain of two inbred strains of mice (BALB/C and C57 BL/6) submitted to a lighting schedule consisting of 12 hr light (0700-1900) and 12 hr darkness (1900-0700). Different mean levels of cAMP were found in each strain. Furthermore, statistical analysis of diurnal brain cAMP fluctuations showed different nycthemeral rhythms in both strains. BALB/C was mainly characterized by the presence of very significant 0600 and 0800 harmonics and C57 BL/6 by an orthophase around 1700 hr. Because both strains were studied under the same experimental conditions of light, temperature and food availability, these factors cannot account for the observed differences, which were thus tentatively interpreted in terms of genetic regulatory processes.

Animals↗
PubMed1982

Glucose utilization increases in choroid plexus during slow wave sleep. A [14C] deoxyglucose study in the cat.

Glucose utilization (GU) was measured during spontaneous waking and slow-wave sleep (SWS) by adaptation of the [14C]deoxyglucose method to the unrestrained cat. In sleeping animals a greater autoradiographic signal between choroid plexus (CP) and the rest of brain was noticed. Quantification provided an index of the metabolic rate of CP and confirmed that mean values for GU were significantly higher in "sleeping' than in "awake' cats.

Animals↗
PubMed1982

Alterations in tyrosine hydroxylase activity elicited by raphe nuclei lesions in the rat locus coeruleus: evidence for the involvement of serotonin afferents.

The time course of the variations in tyrosine hydroxylase (TH) activity was measured in the rat locus coeruleus (LC) after lesions of the nucleus raphe dorsalis (NRD), nucleus raphe centralis superior (NRCS) and nucleus raphe pontis (NRP). A certain number of lesions were performed in the raphe magnus (RM), the caudal and rostral NRP and the caudal and rostral NRCS, lateral to raphe nuclei and in adrenalectomized animals. The serotonin (5-HT) content in the LC was also determined after these lesions. Only raphe nuclei producing significant decreases in the 5-HT content in the LC are successful in provoking increases in the TH activity in the LC, thus these results suggest that the noradrenaline (NA) synthesis in the LC may be regulated by 5-HT afferents. Moreover, intraventricular injections of 5,6-dihydroxytryptamine (5,6-DHT) and administration of parachlorophenylalanine (PCPA) also produce significant increases in TH in the LC. After immunotitrations of TH in the LC it was shown that, with exception of a high dose of 5,6-DHT (75 micrograms), all these treatments provoke an increase in the concentration of the enzyme. It therefore seems that one of the functional roles of 5-HT in the LC could be the regulation of the concentration of TH.

5,6-Dihydroxytryptamine↗
PubMed1980

Genetic studies of daily variations of first-step enzymes of monoamines metabolism in the brain of inbred strains of mice and hybrids. I. Daily variations of tryptophan hydroxylase activity in the nuclei raphe dorsalis, raphe centralis and in the striatum.

A daily variation of tryptophan hydroxylase (TrH) activity was observed in the raphe dorsalis (RD), raphe centralis (RC) and striatum (St) of 3 inbred strains of mice (BALB/c, C57BL/6, C57BR) and of the reciprocal hybrids obtained from Balb/c and C57BL6. Significant differences of the characteristics of these rhythms have been found in the same strain between different structures and for the same structure between different strains. In RD and RC hybridization led to less defined daily variations which, in the striatum, remained well synchronized and could be controlled by a dominant genetic mechanism part. These results help to discuss evidence for selective control mechanisms of regulation responsible for daily variation of TrH in the 5-HT cell bodies and terminals and their relative independence.

Animals↗
PubMed1978

Suprachiasmatic nuclei lesions in the rat: alterations in sleep circadian rhythms.

After continuous control recording (24 h/day) during 5 days, 14 rats received sham, complete or incomplete lesions of the suprachiasmatic nuclei (SCN). Sleep records were analysed from the 22nd to the 27th day after the lesion. In rats with complete lesions of the SCN, there was a strong decrease in the amplitude of the circadian variation in slow wave (SWS) and paradoxical (PS) sleep. The acrophase of SWS remained unaltered whereas that of PS shifted towards the end of the illumination (7.00--19.00 h) period. The importance of these changes in sleep organization seems to be correlated with the size of the SCN lesion.

Animals↗
PubMed1977

Daily variations of various parameters of serotonin metabolism in the rat brain. I. Circadian variations of tryptophan-5-hydroxylase in the raphe nuclei and the striatum.

Daily changes in tryptophan-5-hydroxylase (TrH) activity have been studied in six different 5-HT-containing cell groups (B3, B4, B5, B6, B7, B8,) in the brain stem of rats maintained in a regular cycle of 12 h of light and 12 h of darkness. Significant circadian alternations of TrH activity were observed in most of the raphe nuclei tested, although the changes were not identical from one structure to another. The striatum showed daily variations in TrH activity in opposite phase to the nucleus raphe dorsalis which projects specific terminals into this area. Monoamine oxidase (MAO) activity was simultaneously estimated in these nuclei but did not exhibit and significant rhythm, suggesting a specific regulation of TrH. Total protein levels were also subject to daily changes.

Animals↗
PubMed1977

Daily variations of various parameters of serotonin metabolism in the rat brain. II. Circadian variations in serum and cerebral tryptophan levels: lack of correlation with 5-HT turnover.

Rats submitted to regular 12 h cycles of light and darkness for three weeks were sacrificed at various times of the day. 5-HT, 5-HIAA and tryptophan levels were estimated in the fronto-parietal cerebral cortex. Tyrosine and free and total tryptophan levels in serum were estimated in parallel. Significant circadian variations in 5-HT and 5-HIAA levels were found in cerebral tissues. The peaks of 5-HIAA levels were dectected during the lignt and dark periods respectively, the maximal fluctuations being seen between 17.00 h and 21.00 h, two times separating the light off. Important significant circadian variations in free and total serum tryptophan levels were also observed. In both cases, the maximal levels were found during the middle of the dark phase after the peak of 5-HIAA levels. The circadian rhythm of tyrosine levels in serum was in opposite phase with that of tryptophan (free or total). The diurnal changes in tryptophan content in cerebral tissues seemed thus related to those found in serum. Taking in consideration results obtained in previous studies 16,17 carried out in similar experimental conditions, it was concluded that the parallel increase in serum free tryptophan and in tissues 5-HIAA levels seen during the night were not related to a stimulation of 5-HT turnover. Indeed 5-HT synthesis is minimal at this time16.

Amino Acids↗
PubMed1976

[Circadian rhythms of rat internal temperatures and thermal ambiance (author's transl)].

Chronic recording of cerebellar and subcutaneous temperatures were carried out in rats maintained at different ambient temperatures in a 12 h light-dark cycle (light from 7 to 19 h). Cerebellar and subcutaneous temperatures followed a rhythm with a period of 24 h with acrophase at 1 h and an amplitude of 0.75 degrees C. The amplitude and acrophase were not altered by modification of the ambient temperature (20-25-30-34 or 35 degrees C), but each elevation of ambient temperature produced a rise in the mean internal temperature of the rat. This rise, hardly perceptible at ambient temperatures of 25 and 30 degrees C, reaches 0.5 degrees C between 20 and 25 degrees C and 1 degrees C between 30 and 34 degrees C. This elevation of temperature was maintained for the duration of the 10 days of observation. These results pose at least three questions: the degree of liaison between the rhythms of activity (waking) and temperature; the lability of the mean internal temperature, which alter with ambient temperature while the amplitude of the circadian rhythm is unaltered and the absence of reduction of mean interanl temperature several days exposure to a raised ambient temperature, even when activity and metabolism are reduced by the second day of exposure.

Animals↗