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M Faudon

Publications and source records attributed to M Faudon.

At least 37 records · Page 2Linked to original sources
PubMed1990

Epinephrine in rat hypophysial portal blood is derived mainly from the adrenal medulla.

This study was performed to determine if epinephrine (EPI) present in hypophysial portal blood has a peripheral or a central origin. Pituitary stalk and femoral arterial EPI plasma levels were simultaneously measured in rats anesthetized with thiopental or urethane. EPI was measured by two different methods: radioenzymatic assay or HPLC followed by electrochemical detection. In thiopental-anesthetized rats, levels were higher in hypophysial portal than in femoral arterial plasma with both methods. In urethane-anesthetized rats, no difference in EPI concentrations was found between peripheral and portal plasma. A rapid blood volume depletion (15 ml/kg in 3 min) evoked a marked elevation of pituitary stalk and arterial EPI plasma concentration while norepinephrine (NE) and dopamine (DA) levels were unaffected. Under both types of anesthesia, the increase of EPI levels was higher in peripheral than in portal plasma. After removal of the adrenal glands, EPI was undetectable or barely detectable in pituitary stalk and arterial plasma. The hemorrhage-induced stimulation of EPI secretion was blunted in portal and peripheral plasma of adrenalectomized rats. These findings indicate that: (1) hypophysial portal EPI plasma concentration is highly dependent on an adrenal source; (2) hypothalamic EPI is not released into portal circulation in response to acute hemorrhage, and (3) anesthesia markedly influences catecholamines plasma levels.

Adrenal Medulla↗
PubMed1989

Effect of thalamic parafascicularis nucleus stimulation in regulation of serotoninergic transmission in the cat caudate nucleus: involvement of autoreceptors in the dorsalis raphe nucleus.

The mechanisms involved in parafascicularis nucleus control on serotoninergic neurons projecting into the caudate nucleus were investigated in "encéphale-isole" cats. The effects of unilateral stimulation of the parafascicularis nucleus on the release of newly synthesized [3H]serotonin were simultaneously determined in the ipsilateral caudate nucleus and the dorsalis raphe nucleus using push-pull cannulae. The actions of various pharmacological treatments performed either in the caudate nucleus or in the dorsalis raphe nucleus were also examined. The electrical or chemical stimulation of the parafascicularis nucleus induced a decrease in striatal [3H]serotonin release and an increase in [3H]serotonin release in the dorsalis raphe nucleus. The blockade of cholinergic (mecamylamine) and glutamatergic (PK 26124) transmissions at the striatal level did not modify the thalamic stimulation-induced effect on serotonin release in the caudate nucleus or in the dorsalis raphe nucleus. However, a decrease induced by parafascicularis nucleus stimulation in serotonin release in the caudate nucleus could not be observed when the autoreceptors present on serotoninergic nerve cell bodies localized in the dorsalis raphe nucleus were blocked by a methiothepin perfusion within the nucleus. These results indicate that the parafascicularis nucleus controls striatal serotonin transmission by inducing changes in the nerve activity of serotoninergic neurons in the dorsalis raphe nucleus via somatodendritic serotonin release and autoreceptors.

Animals↗
PubMed1988

Effects of thalamic lesion on the bilateral regulation of serotoninergic transmission in rat basal ganglia.

Unilateral kainic acid lesion of the rat centromedian-parafascicular complex (CM-PF) of the thalamus induced a decrease in the 5-hydroxyindole acetic acid/5-hydroxytryptamine ratio both in ipsi and contralateral striatum and substantia nigra, and an increase in both ipsi and contralateral frontal cerebral cortex. No change in apparent serotonin turnover was detected in anterior raphe nuclei. Serotonin synthesis, estimated by measuring 5-hydroxytryptophan accumulation after injection of a decarboxylase inhibitor, was not affected by the CM-PF lesion. The possible pathways involved in the control of serotonin transmission by CM-PF are discussed.

Animals↗
PubMed1988

In vivo evidence for acetylcholine control of serotonin release in the cat caudate nucleus: influence of halothane anaesthesia.

Using a push-pull cannula technique and an isotopic method for the estimation of [3H]serotonin continuously synthesized from [3H]tryptophan, the effects of acetylcholine were investigated on the in vivo release of [3H]serotonin in the cat basal ganglia and the dorsal raphe nucleus. The unilateral striatal application of acetylcholine (5 x 10(-5) M) reduced local release of [3H]serotonin. This effect was mimicked by nicotine (5 x 10(-5) M) and prevented by mecamylamine (10(-6) M. Oxotremorine (5 x 10(-5) M) had no effect on the local release of [3H]serotonin. All these treatments failed to modify [3H]serotonin release in the ipsilateral substantia nigra or in the dorsal raphe nucleus. The superfusion of serotonergic nerve terminals of the caudate nucleus with tetrodotoxin prevented the inhibitory acetylcholine-induced effect on serotonin release. Furthermore, bicuculline (5 x 10(-5) M) in the caudate nucleus blocked the effect of nicotine, while gamma-aminobutyric acid (10(-5) M) induced a decrease in local release of [3H]serotonin. These data strongly suggest that the inhibitory control exerted by acetylcholine on serotonergic transmission could involve gamma-aminobutyric acid interneurons. Acetylcholine-induced changes in [3H]serotonin release were only observed in non-anaesthetized "encéphale isolé" cats and not in halothane-anaesthetized animals. The possibility that such a regulation could be presynaptic (direct or through other neurotransmitters) or related to a change in the activity of the serotonergic raphe-striatal neuronal system is discussed.

Acetylcholine↗
PubMed1984

Release of serotonin from perikarya in cat nodose ganglia.

Newly synthesized serotonin (5-HT) can be released in the nodose ganglion from the nerve cell bodies of vago-aortic serotoninergic neurones. Free-calcium led to a decrease of spontaneous and potassium-evoked release. The veratridine-stimulating response was abolished by TTX. The concept that 5-HT released from perikarya in the extracellular space could be involved in the self-regulation of the activity of the vago-aortic pathway is discussed.

Animals↗
PubMed1984

In vitro 3H-serotonin (5-HT) synthesis and release in BALBc and C57BL mice. I. Terminal areas.

"In vitro," 3H-5-HT and 3H-5-HIAA newly synthesized from 3H-TRP are measured in the caudate nucleus and the hippocampus of C57BL and BALBc mice. Higher synthesis, utilization and release are to be found in C57BL than in BALBc strain. In the hippocampus of C57BL this higher synthesis is due both to higher tryptophan hydroxylase activity and to higher tryptophan uptake ability. But in the caudate nucleus the initial accumulation of tryptophan is similar in both strains. Finally the two forms of monoamine oxidase (A and B) show also similar activities in both strain. These data will be compared to those obtained at the nerve cell body level in the paper (II).

Animals↗
PubMed1984

In vitro 3H-serotonin (5-HT) synthesis and release in BALBc and C57BL mice. II. Cell body areas.

"In vitro" 3H-5-HT and 3H-5-HIAA, newly synthesized from 3H-TRP, are measured in the brainstem, the anterior raphe nuclei and the locus coeruleus of C57BL and BALBc mice. As found for the caudate nucleus and the hippocampus, higher synthesis and release are determined in C57BL than in BALBc, for the locus coeruleus and more globally, for the brainstem. But these differences disappear when the study is carried on the raphe dorsalis and the raphe centralis nuclei. Therefore the serotonergic activity could be independently regulated at the level of cell bodies and at those of terminals. However, the 5-HT metabolism of NRD of BALBc mice could be submitted to a specific autoinhibition which could explain a lower 5-HT synthesis and release at the corresponding terminal level, compared to C57BL.

Animals↗
PubMed1982

Uptake of [3H]serotonin and [3H]noradrenaline in the raphe nuclei and the locus coeruleus of C57BL/6 Rholco and BALB/c Cenlco mice at three times of the day.

Uptake of [3H]serotonin (5-HT) and [3H]noradrenaline (NA) in the raphe nuclei and the locus coeruleus of C57BL/6 and BALB/c mice has been analysed at 3 times of the day. Daily mean results clearly show a higher uptake of [3H]5-HT and [3H]NA in the raphe dorsalis of the BALB/c strain than in C57BL/6. A higher uptake of [3H]NA is also found in the locus coeruleus of BALB/c mice than in C57BL/6. However, differences between the strains are neither visible at all times of the day nor simultaneously in the different structures.

Aging↗
PubMed1982

In vivo release of serotonin in two raphe nuclei (raphe dorsalis and magnus) of the cat.

The release of 3H-serotonin (3H-5-HT) endogenously synthesized from 3H-tryptophan was estimated in both dorsalis and magnus (MRN) raphe nuclei of anaesthetized "encéphale isolé" cats, by using push-pull cannulae. Resting steady state in the release of 3H-5-HT was observed 30 min after the beginning of superfusion with L-3H-tryptophan. The amounts of 3H-5-HT released in the DRN and the MRN are much greater than those measured simultaneously in the caudate nucleus. A marked increase either in the 5-HT release was seen in the presence of fluoxetine, a potent reuptake blocker of 5-HT, or during local depolarization with potassium chloride. The spontaneous release was diminished by removing Ca++ and by adding cobalt to the medium. Tetrodotoxin (TTX) decreased the 5-HT release in the DRN and, based on previously established, blocked the stimulating effect of batrachotoxin. According to the pharmacological characteristics of the monoamine dendritic release determined for dopamine in the substantia nigra [17], our results suggest that 5-HT release processes in the DRN correspond to a release from nerve endings, not from dendrites. The purpose of this study was to determine if the 5-HT released in the DRN is released from either axon terminals or dendrites. Morphological studies performed on the DRN do not consistently demonstrate the high density of serotoninergic varicosities in the DRN. In addition, two types of 5-HT axonal varicosities, characterized by their synaptic or non-synaptic junctions, are present in the brain. The concept that the quantities of 5-HT released could vary from one type compared to the other is discussed.

Animals↗
PubMed1982

Daily variations in serotonin metabolism in the suprachiasmatic nucleus of the rat: influence of oestradiol impregnation.

In order to determine the temporal relationships between variations in 5-hydroxy-tryptamine (5-HT, serotonin) metabolism in the suprachiasmatic nucleus (SCN) and the cyclic LH surge, and also to check whether implantation of oestradiol capsules might modulate 5-HT metabolism in the SCN, we carried out a parallel study of 5-HT content in the SCN and median eminence, and 5-HT metabolism in the SCN and supraoptic region in vitro. These experiments were performed on intact male rats, ovariectomized females and ovariectomized females implanted with oestradiol. It was only in ovariectomized rats implanted with oestradiol, in which we have described the existence of a clear-cut circadian rhythm of LH secretion, that we found fluctuations in the content, synthesis and utilization of 5-HT. The content and synthesis were characterized by a peak between 12.00 and 15.00 h, whereas utilization was 50% higher at 09.00 and 19.00 h than at 15.00 h. These fluctuations in 5-HT content and metabolism were specific to the SCN; the median eminence and the supraoptic region did not show such variations. They were also specific to ovariectomized rats implanted with oestradiol, since the patterns of 5-HT content and metabolism in the SCN were the same in males and ovariectomized females and did not differ from those in the median eminence, the supraoptic region or the whole hypothalamus. These results suggest that 5-HT terminals in the SCN play an important role in the control of cyclic LH secretion at a critical period. Moreover, oestradiol seems to be partly responsible for the fluctuations of 5-HT metabolism in the SCN of ovariectomized rats implanted with oestradiol.

Animals↗
PubMed1981

5-HT metabolism in the intestinal wall of the rabbit.

The levels of TRP, 5-HTP, 5-HT and 5-HIAA were measured in the proximal colon of the rabbit using ion exchange chromatography and spectrofluorimetry. Assays were performed on fragments of the intact colonic wall, on the muscle layers containing nerve plexuses, and on the mucosa-containing enterochromaffin cells. In spite of identical TRP concentration, 5-HT levels were higher in the mucosa than in the muscle containing nerve plexus. In the muscle, the ratio 5-HIAA/5-HT was about 1, i.e., comparable to that of the brain, whereas the ratio was very low in the mucosa, suggesting a weak 5-HT catabolism in the enterochromaffin cells. When the mucosa was severed from the muscle, 5-HT synthesis was increased. In this case, 5-HT and 5-HIAA concentrations in the reconstituted wall (muscles + mucosa) were higher than in the intact wall. In in vitro studies, levels of newly synthesized (3H)5-HT from (3H)TRP were 3 times higher in the reconstituted wall than in the intact one, and the conversion index of TRP to 5-HT was higher in the mucosa and in the reconstituted wall respectively. These results suggest that enterochromaffin cells do synthesize 5-HT from TRP when the mucosa is divided from the muscle. (3H)5-HT was taken up by both nerve plexuses and mucosa, with a high affinity mechanism. Results from tryptophan loading experiments indicated that 5-HTP decarboxylase in the gut might be involved in the regulation of 5-HT synthesis. The mucosa severed from the muscles might represent a good model for the study of carcinoid tumour development.

5-Hydroxytryptophan↗
PubMed1981

[Kinetic study of serotonin metabolism in the suprachiasmatic nucleus of the rat: neuroendocrine incidence (author's transl)].

The suprachiasmatic nucleus (SCN), which is implicated in the regulation of several cyclic neuroendocrine rhythms, displays a conspicuous and apparently specific serotoninergic innervation. Our study was intended to establish more precise correlations between the incidence of serotonin (5 HT) metabolism in the activity of the SCN, and neuroendocrine rhythms. For this purpose, castrated female rats, having subcutaneous implants of estradiol, were studied. These animals display very marked circadian fluctuations in plasma levels of the pituitary hormones ACTH, LH and PRL; a relatively well-synchronized increment in all these hormones occurs between 11.00 and 15.00. Punches were obtained to determine the endogenous content of 5 HT, measured by a radioenzymatic technique, simultaneously in SCN and median eminence (ME). An index of SCN activity was determined from in vivo SCN 2-deoxy (1-14C) glucose (DG) uptake; the retention was estimated on radioautographs. Endogenous level of 5 HT displayed a marked circadian rhythm with a peak between 12.00 and 15.00 in the SCN; 5 HT levels were constant throughout the day in the ME. 14C-DG uptake was greater at 15.00 than at 9.00. However, after PCPA treatment or raphe lesions, the uptake of 14C-DG was the same at 9.00 and 15.00. Taken together, these results strongly suggest that in our model: (1) SCN displays a rhythm of activity in the light period; (2) SCN displays specific rhythms in the content of 5 HT; (3) the SCN rhythm of activity must be under an inhibitory control of 5 HT, since the lowest metabolic level is increased at 9.00 by inactivation of 5 HT system; (4) the close relationships between the initial release phase of several pituitary hormones, the increase of metabolic activity in the SCN and the higher level of the 5 HT in the nucleus suggest that 5 HT terminals in the SCN play an important part in the control of cyclic hormonal secretion.

Adrenocorticotropic Hormone↗
PubMed1981

Comparison of brain serotoninergic systems in C57BL and BALBc mice during development.

Adult C57BL and BALBc mice will exhibit differences in behaviour and in their sleep patterns which may be correlated with monoamine content. In this study, we measured the endogenous levels of serotonin (5-HT), tryptophan (TRP), 5-hydroxyindole acetic acid (5-HIAA), noradrenaline (NA) and dopamine (DA) in the forebrain and hindbrain regions of these strains of mice from day 1 to 12 weeks of age. Using the micropunch technique and a radioenzymatic method, we also determined the endogenous 5-HT levels in the nuclei raphe dorsalis, centralis, magnus-pallidus and obscurus. During development, NA levels in the brain stem are higher in the C57BL than in the BALBc mice. From 5 weeks of age onwards, the levels of 5-HT, DA and NA in the forebrain are also higher in the C57BL mice. However, no differences in 5-Ht and DA content was found for the brain stems of these two strains. When the 5-HT levels in the different raphe nuclei were analyzed, the nucleus raphe dorsalis of the BALBc showed a higher 5-HT content.

Aging↗
PubMed1980

Distribution of choline acetyltransferase in the brain stem of the cat.

Activities of choline acetyltransferase were detected in various structures of the brain stem of the cat by radiochemical methods on square punches of fresh tissue. High activities were measured in all cranial motor nuclei and in reticular nuclei such as the gigantocellular tegmental nucleus. Low activities were found in sensory nuclei and in the pyramidal tract, trapezoïd body and inferior and superior olive complex. Raphe nuclei, that also contain serotonergic neurons, exhibit relatively high activities of choline acetyltransferase. In spite of some exceptions, the results are in good accordance with those previously obtained by histochemical methods for acetylcholinesterase.

Animals↗
PubMed1979

5-HT concentration in cat's brain.

Endogenous concentrations of TRP, 5-HT and 5-HIAA were determined in the different cortical and subcortical areas of adult cat's brain, using ion-exchange chromatography and spectrofluorimetric methods. Tryptophan is homogeneously distributed in all structures of the brain. 5-HT is mainly accumulated in the brain stem, hypothalamus and caudate nucleus, but also in cortical areas as olfactory and piriform gyrus. The ratio 5-HIAA/5-HT shows that 5-HT utilization is higher in the structures containing small amounts of 5-HT. Using the radioenzymatic assay described by Saavedra et al. (1973), the rostrocaudal distribution of 5-HT content was determined in olfactory and piriform cortex. Important concentrations of 5-HT were detected in the prepiriformis and anterior amygdaloidea areas. Using the same assay and microdissection on frozen frontal slices of the brain, the distribution of 5-HT concentration throughout the different layers of cortical areas was studied. Piriform, olfactory and sigmoid cortex present high concentrations in the superficial layers, including the molecular one. These results were confirmed by uptake studies, made on crude homogenates from frozen tissue, suggesting that 5-HT is mainly contained in the most external cortical terminals.

Animals↗