Biomedical subjects

J F Pujol

Publications and source records attributed to J F Pujol.

At least 73 records · Page 4Linked to original sources

PubMed1987

Benzodiazepine binding sites in the cingulate cortex after lesion of the noradrenaline and dopamine containing afferents.

The distribution of benzodiazepine binding sites was analysed in the cingulate cortex of the rat brain by quantitative radioautography of brain sections incubated with a full agonist benzodiazepine ligand, 3H-flunitrazepam (3H-FLU), or with a partial agonist with non benzodiazepine structure, (7-3H)-4hydroxy-N(4,5-dihydroxy-2-thiazolyl)-6 methoxy-3-quinoline (3H-RU 43028), after lesion of noradrenaline (NA) and dopamine (DA) containing afferents to this structure. NA denervation was obtained by systemic administration of N-(2-chlorethyl)-N ethyl-2-bromobenzylamine (DSP4) and destruction of both NA and DA containing afferents was induced by unilateral injection of 6-hydroxydopamine (6-OHDA) in the middle forebrain bundle (MFB). A similar caudo-rostral pattern of distribution was found in the cingulate cortex after incubation with these two ligands which bound a greater number of sites in the anterior portion of the structure. In spite of a very precise anatomical sampling (200 micron intervals along the postero-anterior axis) no significant difference was observed when intact and lesioned brains were compared. It is concluded that benzodiazepine binding sites eventually localized on catecholaminergic afferents to the cingulate cortex do not represent a significant proportion of the total population of these sites in this structure.

Afferent Pathways↗

PubMed1987

Inhibition of tyrosine hydroxylase activity by serotonin in explants of newborn rat locus ceruleus.

The long-term regulation of tyrosine hydroxylase (TH) by serotonin has been studied with cultures of newborn rat locus ceruleus explants. The presence of serotonin in the culture medium for a 24-h period was followed by an inhibition of TH activity in the explants. This effect lasted several days, with a maximal effect 2 days after treatment. Moreover, the decrease was reversible and dependent on the concentration of serotonin used (from 1 microM to 1 mM). The mechanisms of this regulation have been studied using drugs such as those known to act specifically on serotoninergic receptors and those known to interfere with protein synthesis. Thus, the action of serotonin (10(-5) M) on TH activity was suppressed with equimolar concentrations of serotoninergic antagonists such as metergoline or methiothepin. It was reproduced by quipazine, a drug capable of acting as a serotoninergic agonist. Inhibitors of protein synthesis acting either at the transcriptional or the translational levels can reproduce the inhibition of TH activity by serotonin alone. Furthermore, the effects of one or the other of these compounds and that of serotonin were not additive. This study confirms the hypothesis of an inhibitory control by serotonin on TH activity in the noradrenergic neurons of the locus ceruleus. Serotonin could regulate the synthesis of the enzyme through specific serotoninergic receptors.

Amanitins↗

PubMed1987

Regional distribution of high-affinity gamma-[3H]hydroxybutyrate binding sites as determined by quantitative autoradiography.

The distribution of high-affinity binding sites for gamma-[3H]hydroxybutyrate in coronal sections of rat brain was studied by quantitative autoradiographic techniques. Binding sites for this naturally occurring substance, which may possibly have a neurotransmitter role, are concentrated in some restricted areas of the brain, particularly in the limbic system. The hippocampus (especially field CA1 of Ammon's horn, at 292 fmol/mg of tissue), septum (72 fmol/mg of tissue), and cortex (frontal, 113 fmol/mg of tissue; parietal, 103 fmol/mg of tissue; cingulate, 114 fmol/mg of tissue; and entorhinal, 134 fmol/mg of tissue) show pronounced labeling with gamma-[3H]hydroxybutyrate. Binding is much lower in caudatus-putamen (50 fmol/mg of tissue), thalamus, and hypothalamus. Caudal parts of the brain (cerebellum, pons, and medulla) are practically devoid of binding sites. These results strongly support a functional role of endogenous gamma-hydroxybutyrate in particularly restricted areas of the rat brain.

Animals↗

PubMed1987

The ability of the alpha 2-adrenergic agonist clonidine to suppress central noradrenergic hyperactivity secondary to hemodynamic or environmental stimuli.

Metabolism of catecholamines was monitored by in vivo voltammetry in the ventrolateral medulla (encompassing the A1 group of noradrenergic cell bodies) of anesthetized rats and in the locus coeruleus of behaving rats. Activation of metabolism of catecholamines was produced by using: (1) controlled hypotension (sodium nitroprusside, mean arterial pressure reduced to approximately 60 mm Hg for 60 min, n = 5) in anesthetized animals; and (2) immobilization (10 min) of conscious rats (n = 5). Clonidine, 200 micrograms/kg (i.p., n = 3), suppressed almost entirely the activation of the metabolism of catecholamines secondary to controlled hypotension in the ventrolateral medulla. Clonidine, 50 (n = 3) to 200 (n = 5) micrograms/kg (i.p.), produced a dose-dependent suppression of the activation of the metabolism of catecholamines induced by immobilization in the locus coeruleus of conscious rats. The results obtained from this study provide a biochemical rationale for the use of alpha 2-agonists in conditions where central or peripheral noradrenergic activity is heightened.

Animals↗

PubMed1986

Distinct functions for dopamine and serotonin in locomotor behaviour: evidence using the 5-HT1 agonist RU 24969 in globus pallidus-lesioned rats.

The locomotor effect of RU 24969, a potent 5-HT1 agonist, was tested in two experimental conditions. Firstly, 5-HT neurons were degenerated by i.c.v. infusion of 5,7-dihydroxytryptamine (5,7-DHT). Secondly, outputs of the nigrostriatal and mesolimbic dopaminergic (DAergic) systems were bilaterally disrupted by electrolytic lesion of the globus pallidus (GP). After both types of lesion, RU 24969 (1.25-5 mg/kg, i.p.) induced an intense and long-lasting hyperlocomotion which was more pronounced than in intact rats. The hyperlocomotion induced in 5,7-DHT lesioned rats as well as that in intact rats was abolished by the DA blocker haloperidol (0.5 mg/kg, i.p.). On the contrary the hyperlocomotion induced in GP-lesioned rats was either unmodified or increased both by haloperidol even at a very high dose (2 mg/kg, i.p.) and by methysergide (5 mg/kg, i.p.). It is concluded that (i) there is no DAergic link in the locomotor response to RU 24969, (ii) 5-HT1 receptors are involved in the motor execution of locomotion, (iii) DA initiates and controls the 5-HT-mediated locomotion in normal rats.

Animals↗

PubMed1986

Catecholamine metabolism in the rat locus coeruleus as studied by in vivo differential pulse voltammetry. III. Evidence for the existence of an alpha 2-adrenergic tonic inhibition in behaving rats.

One of the various regulations controlling the noradrenergic (NA) locus coeruleus (LC) activity has been proved to be alpha 2 adrenergic specific, on the basis of electrophysiological data obtained in anesthetized preparations. To assess, under rigorously chronic conditions, the existence of such an inhibition, recordings of LC catechol metabolic activity were performed with in vivo differential pulse voltammetry. A guiding cannula and appropriate wires were implanted under anesthesia. After 48 h of recovery a carbon fiber electrode was threaded to the LC through this cannula to monitor the LC catechol oxidation current. Piperoxane 60 mg/kg i.p. and yohimbine 10 mg/kg i.p. induced an increase in catechol oxidation current to approximately 300% of baseline (100%) values. Graded doses of piperoxane (1-100 mg/kg i.p.) induced a dose dependent increase in LC catechol metabolic activity (ED50 = 29.7 mg/kg). These changes in catechol oxidation current were confirmed either by combined electrophysiological and electrochemical recordings in the LC of an anesthetized preparation, or by postmortem HPLC catechol determinations on LC microdissections. By contrast, guanfacine 1 mg/kg and clonidine (10-200 micrograms/kg i.p.) induced a dose dependent decrease in catechol peak height. Clonidine 50 micrograms/kg reversed the effect of piperoxane 30 mg/kg i.p. On the other hand, a highly selective alpha 1 antagonist, such as prazosin (1 mg/kg i.p.), evoked only a small increase in catechol peak (11% above saline effect). This data is consistent with previously reported electrophysiological, biochemical and autoradiographic data. They confirm the presence of a tonic alpha 2 adrenergic inhibition on NA-LC cell activity, in behaving rats.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1986

Clonidine modulates locus coeruleus metabolic hyperactivity induced by stress in behaving rats.

To assess, under rigorously chronic conditions, whether clonidine would modulate the increased activity engendered by stress in the locus coeruleus (LC), rats implanted for recordings by in vivo voltammetry, were subjected to immobilization (10 min). When injected 30-60 min before stress, clonidine 50-200 micrograms/kg i.p. modulated the increased catechol metabolic activity in a dose-dependent manner. This provides a biochemical basis, obtained in behaving rats, for using clonidine as a stabilizer in syndromes where central noradrenergic or peripheral sympathetic activities are heightened.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1986

Variations in 3,4-dihydroxyphenylacetic acid concentration are correlated to single cell firing changes in the rat locus coeruleus.

The purpose of this study is to see whether variations in the catechol oxidation peak in the locus coeruleus would be closely related with variations in single cell firing, and would be independent of the mechanism triggering the variation of neuronal activity. Single unit and electrochemical (differential pulse voltammetry) recordings were performed, respectively on the left and right locus coeruleus of anaesthetized rats. The variations in single unit activity were induced using well known stimulatory mechanisms (yohimbine, hypovolemia, indirect activation using a 5-hydroxytryptamine central agonist RU 24969, RU 24722 known to activate noradrenergic metabolism), or inhibitory (clonidine, morphine) models. This was done in addition to successive activation or inhibition (reversal of oxotremorine with scopolamine, antagonism of clonidine by piperoxane). In all the experimental conditions, variations in the catechol oxidation current followed variations in single cell activity. Furthermore, the catechol oxidation current variations correlated significantly to changes in the firing rate. Such a close correlation between a catechol oxidation peak, and the electrical activity of the locus coeruleus cell bodies supports the use of catechol oxidation current variations as a good indirect index of functional activity in noradrenergic locus coeruleus perikarya. This suggests a close relationship between dopamine metabolism and electrical activity in locus coeruleus cell bodies.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1986

Benzodiazepine binding sites: localization and characterization in the limbic system of the rat brain.

The distribution of benzodiazepine binding sites was analysed in limbic structures of rat brain by quantitative radioautography of brain sections incubated with 3H-flunitrazepam (3H-FLU). Quantitative estimation of the binding parameters was made in each range of postero-anterior sections taken. Distribution of 3H-FLU binding sites was found to be rather homogeneous in most of the structures examined but there were regional differences which resulted from variations in the densities of sites rather than in their affinities. A particular distribution pattern of 3H-FLU binding sites was observed in the cingulate cortex contrasting with the homogeneous postero-anterior distribution measured in other cortical areas in the same slices. A significantly greater density of sites was found in the anterior part of the structure as compared to the posterior part. This difference, which corresponds to a change in the density of sites without alteration of their apparent affinity and occurs at a precise anatomical level, is discussed with reference to the anatomical organization of this brain structure and to its possible functional implications.

Animals↗

PubMed1985

Effects of D- and L-amphetamine on dopamine metabolism and ascorbic acid levels in nucleus accumbens and olfactory tubercle as studied by in vivo differential pulse voltammetry.

Differential pulse voltammetry used together with electrochemically pretreated carbon fibre microelectrodes allowed us to detect in vivo two well-separated peaks in nucleus accumbens and olfactory tubercle. The two peaks situated at -50 mV (peak 1) and + 100 mV (peak 2) correspond, respectively, to the oxidation current of the ascorbic acid and to the oxidation current of the 3,4-dihydroxyphenylacetic acid (DOPAC). The experiments were carried out on anesthetized rats. Voltammograms were recorded in nucleus accumbens and olfactory tubercle every minute alternately in each structure. In control conditions, peak 1 height was greater in olfactory tubercle than in nucleus accumbens and peak 2 height was greater in nucleus accumbens than in olfactory tubercle. Both isomers of amphetamine induced a decrease of the peak 2 height in the two structures. The decrease was greater in olfactory tubercle. Higher doses of L-amphetamine were required to induce peak 2 height decrease of the same extent. Both isomers induced a marked increase of the peak 1 height in nucleus accumbens whereas peak 1 height in olfactory tubercle was slightly augmented. D-amphetamine was more effective than L-amphetamine in increasing peak 1 height.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1985

Effect of haloperidol and sulpiride on dopamine metabolism in nucleus accumbens and olfactory tubercle: a study by in vivo voltammetry.

Differential pulse voltammetry used with electrochemically pretreated carbon fibre microelectrodes enables separation between the two peaks corresponding to the ascorbic acid and catechol oxidation currents. The effects of haloperidol and sulpiride on the 3,4-dihydroxyphenylacetic acid peak recorded in the nucleus accumbens and olfactory tubercle of rats were studied. Chloral hydrate anaesthetized preparations and chronic preparations were used. A microdevice was designed to implant electrodes in freely moving rats. Voltammograms were recorded every minute in each structure in acute preparations and every 2 min in chronic preparations. In acute preparations haloperidol induced a similar dose-dependent increase in the catechol oxidation peak in both structures. Sulpiride at all doses only induced an increase in the olfactory tubercle. In chronic preparations haloperidol and sulpiride had even larger effects on the 3,4-dihydroxyphenylacetic acid peak in both regions. In these preparations sulpiride induced a significant increase in nucleus accumbens. The effects induced by haloperidol in the two regions were greater than those induced by sulpiride. The main conclusions of this study are that the results of voltammetry agree with biochemical results on the effects of haloperidol and sulpiride on dopamine metabolism. An interaction of chloral hydrate with the effects of the two neuroleptics was also observed.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1985

[Differential voltametry: a new method for studying the cerebral metabolism of monoamines].

In vivo electrochemistry by differential pulse voltammetry represents an interesting option for functional neurochemistry or neuropharmacology. This paper successively presents the principle of the method and the technical bases of the measurement. The particular points of the specificity of the method and the necessary identification procedure of the different species detected in vivo are discussed (see fig. 1 to 7) with special reference to the detection of ascorbic acid and catechol compounds. Success for analysis of 5-hydroxy-indolic compounds are also referenced. In a second part of the paper an example of an in vivo metabolic exploration is presented. The detection of a catechol compound in the rat locus coeruleus, its identification as being extracellular DOPAC, its origin in noradrenergic cell bodies, its relationship with the activity of this group of noradrenaline containing perikarya are discussed (see fig. 8 to 15).

3,4-Dihydroxyphenylacetic Acid↗

PubMed1984

Identification of catecholamine cell bodies in the pons and pons-mesencephalon junction of the cat brain, using tyrosine hydroxylase and dopamine-beta-hydroxylase immunohistochemistry.

Using a double labeling immunohistochemical method with antibodies to tyrosine hydroxylase and dopamine-beta-hydroxylase, we reexamined the topographical distribution of dopaminergic (DA) and noradrenergic (NA) cells in the pons-mesencephalon junction of the cat. Besides DA cells of SN and its extensions, DA cells were also observed more caudally in nucleus raphe linearis intermedius and dorsalis, decussation of brachium conjunctivum, fasciculus longitudinalis medialis and periaqueductal gray. In nucleus locus coeruleus, cells exhibited variable levels of DBH, but dopaminergic cells were not evidenced in this structure.

Animals↗

PubMed1984

Neuron-specific enolase in cerebrospinal fluid: a possible indicator of neuronal damage in kainic acid lesions.

The presence of the neuron specific enolase (NSE) has been tested by sandwich enzyme immunoassay in cerebrospinal fluid (CSF) of rats after intrastriatal injection of various amounts of kainic acid (KA). Incremental release of NSE was observed in CSF for increasing concentrations of injected KA. Still, a significant decrease of NSE striatal content was detected only with the two maximal amounts of KA infused. These data indicate that measurements of NSE in CSF might be a more sensitive index of neuronal damage than the actual assay within the tissue, and also present the advantage of being a non-invasive method of investigation.

Animals↗

PubMed1984

Effect of local 5,6-dihydroxytryptamine on the rat olfactory bulb responsiveness during wakefulness and sleep.

This study investigated a possible participation of the centrifugal serotonergic (5-HT) innervation of the olfactory bulb (OB) in the control of the multiunit mitral cell responsiveness in behaving rats. A bilateral injection of 5,6-dihydroxytryptamine solution (5,6-DHT) into the OB induced in this structure an average 70% reduction in the level of endogenous serotonin. Control and treated animals were habituated to eat a single 2 h daily meal. Recording sessions were performed either after a 22 h fasting period or just after the meal. The summated multiunit mitral cell activity and vigilance state parameters were recorded in the absence of and during repeated stimulation by puffs of food odour and isoamyl acetate. The results showed that the 5,6-DHT treatment did not modify significantly previously established centrifugal controls exerted at the OB level: (1) the selective enhancement of the mitral cell responsiveness to food odour occurring in waking food-deprived animals; (2) the inhibition of the olfactory input during slow wave sleep. However, the considered 5-HT projections could mediate some inhibitory influence on mitral cell activity during wakefulness only. Finally, the 5-HT innervation of the OB did not seem to be involved in basic mechanisms of olfactory recognition.

5,6-Dihydroxytryptamine↗

PubMed1984

Experimental brain ischemia: neuron-specific enolase level in cerebrospinal fluid as an index of neuronal damage.

Levels of neuron-specific enolase (NSE) were measured in rat CSF following occlusion of the four major arteries to the brain for 10, 20, or 30 min. In the CSF of rats submitted to 30 min of total ischemia, an up to nine-fold increase of NSE level occurred within the first few hours and then slowly diminished. Significant levels were seen for as long as 8 days. Histological observations 3 days after ischemia showed neuronal loss as well as neuronal damage in several forebrain regions such as hippocampus, striatum, and thalamus. Ischemia was followed by transient decreases in exploration behavior and neurological states that were no longer visible 24 h later. After 10 or 20 min ischemia, NSE levels were increased to a lesser degree and fewer damaged neurons were observed. The positive correlation between duration of ischemia and amount of NSE release in CSF indicates that the measurement of NSE in the CSF is a sensitive and reliable index of neuronal lesions.

Animals↗

PubMed1984

Immunohistochemical study of the catecholaminergic systems in the lower brain stem of the human infant.

The study of catecholaminergic (CA) systems in the lower brain stem was undertaken in the infant. A method of indirect immunohistofluorescence using antibodies to tyrosine-hydroxylase (TH) was applied to five brains from infants whose deaths had no neurological cause; two brains were submitted to fully systematic investigation. A topographical and morphocytological analysis of the CA systems was carried out on horizontal serial sections. A neuronal map is shown presenting four bulbar and four pontine sections. The disposition of the main CA groups (i.e. A1, A2, locus coeruleus) was found to be consistent with the data provided by the literature concerning the human foetus and the adult. Topographic differences and peculiarities are emphasized in the infant. Mapping of phenylethanolamine N methyltransferase (PNMT) positive neurons was performed in one plane of section of mid-medulla. This technique might usefully be applied to the exploration of putative diseases of bulbopontine CA systems, such as the sudden infant death syndrome and central blood pressure disorders.

Brain Mapping↗

PubMed1983

Cholinergic control of catechol metabolism in the rat locus coeruleus as studied by in vivo voltammetry.

Differential pulse voltammetry with treated carbon fibre electrodes was used to study the effect of cholinergic drugs on the metabolism of locus coeruleus (LC) noradrenergic cells in vivo. A catechol peak corresponding to DOPAC synthesized by noradrenergic cells and reflecting their metabolic activity, was recorded every two minutes in the LC of freely moving rats. Cholinergic agonists like eserine (0.5 mg/kg s.c.) and oxotremorine (0.1 and 0.4 mg/kg s.c.) increased the DOPAC peak. This effect seemed to be mediated by muscarinic receptors since it was antagonized by scopolamine (5 mg/kg i.p.). Oxotremorine in high doses (1.5 mg/kg s.c. for 3 days) induced 'delayed activation' of tyrosine hydroxylase (+273%). In these conditions LC cells were no longer responsive to a challenge dose of oxotremorine though they maintained normal responsiveness to noradrenergic drugs. The results show that cholinergic drugs can greatly influence the metabolism of LC noradrenergic neurons.

3,4-Dihydroxyphenylacetic Acid↗