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Y Lamour

Publications and source records attributed to Y Lamour.

At least 55 records · Page 3Linked to original sources
PubMed1990

Regional distribution of 3-O-methyl-DOPA in the cortex and subcortical structures in the rat: effect of aging.

Dihydroxyphenylalanine (DOPA) and its metabolite 3-O-methyl-DOPA (3-OMDOPA) have been identified as normal constituents in blood, CSF and brain in human and several animal species. In the present study, we report results of 3-OMDOPA measurements in seven cortical areas, hippocampus and striatum of young (3-month-old), middle aged (10-month-old) and aged (27-month-old) rats. 3-OMDOPA was identified in all the areas considered. Regional differences were observed, with the highest levels being found in the hippocampus and the somatomotor and pyriform cortex. A marked increase in the level of 3-OMDOPA was observed in all the cortical areas and in the hippocampus of aged rats. In contrast, this level remained unchanged in the striatum. These modifications were compared to those observed in the levels of dopamine (DA) in the same areas.

Aging↗
PubMed1990

Effects of acetylcholine on single cortical somatosensory neurons in the unanesthetized rat.

Experiments have been performed on unanesthetized rats using a chronic restraint system. The animal's head was held in a stereotaxic apparatus by means of two metallic tubes fixed on the skull with dental cement. Electrodes consisted of a recording micropipette (filled with 1 M NaCl and 2% Pontamine Blue) attached to a multibarreled micropipette for iontophoresis. Electrode penetrations were reconstructed on camera lucida drawings of frontal brain sections. The overall percentage of spontaneously active somatosensory neurons was 77% with a mean spontaneous activity of 5.9 impulse/s (n = 405). Yet differences were observed in the proportions of active cells as well as in the mean spontaneous activity between cortical layers (both parameters being significantly higher in layers V and VI). Comparison with results obtained under urethane anesthesia [Dykes R. W. and Lamour Y. (1988) J. Neurophysiol. 60, 703-724] shows that the percentage of the spontaneously active neurons and the mean spontaneous activity were both significantly higher in unanesthetized rats (77 vs 36%; 5.9 vs 2.6 impulse/s). Nevertheless, the laminar distribution of the most active cells was similar under both conditions. In the present study, 52.3% of the neurons (n = 380) were excited by acetylcholine and 46% (n = 198) by carbachol. Significantly larger percentages of neurons excited by acetylcholine were found in layers Vb and VIb. These effects of cholinergic agonists--observed for the first time in unanesthetized rats--differed significantly from those previously obtained under anesthesia (33 and 34% of neurons excited by acetylcholine and carbachol, respectively) [Lamour Y. et al. (1982) Neuroscience 7, 1483-1494].(ABSTRACT TRUNCATED AT 250 WORDS)

Acetylcholine↗
PubMed1990

Effects of iontophoretically applied monoamines on somatosensory cortical neurons of unanesthetized rats.

The response of somatosensory cortical neurons to iontophoretic applications of monoamines was studied in unanesthetized rats. The animal's head was held in a stereotaxic apparatus by means of a painless head-restraining system implanted 8 days prior to the recording sessions. The electrodes consisted of a recording micropipette attached to a multibarreled iontophoresis micropipette. The electrode penetrations were reconstructed on camera lucida drawings of frontal brain sections. The percentage of cortical neurons responding to application of monoamines were 76% after noradrenaline, 58% after dopamine and 66% after serotonin. The differences observed among percentages of responses seemingly correlate with the relative abundance of terminal axons and receptors for each of the three monoamines in the somatosensory cortex. The vast majority of the responding neurons were inhibited by monoamines and this inhibitory effect was independent of the level of spontaneous activity. The depressant effect of the monoamines on glutamate and acetylcholine-evoked responses supports a modulatory role for these substances. Serotonin was the most potent, followed by noradrenaline and dopamine. The present study shows that when the influence of anesthesia is eliminated, the predominant effect of monoamines on cortical first somatosensory neurons is one of inhibition. These findings contrast with results obtained under some anesthetic conditions, as well as under in vitro conditions.

Acetylcholine↗
PubMed1990

Neuronal localization of the nerve growth factor precursor-like immunoreactivity in the rat brain.

The distribution of the nerve growth factor precursor(proNGF)-like immunoreactivity was examined in the adult rat brain with affinity-purified antisera directed against synthetic peptides that reproduce sequences of the precursor protein. Immunoreactivity was localized in defined areas of the neocortex, hippocampal formation, thalamus/hypothalamus, striatum, olfactory bulb, pons and spinal cord, which are regions previously reported to contain NGF mRNA. Interestingly, immunoreactivity was also observed in the septum and diagonal band of Broca known to contain very low NGF mRNA levels. Using immunohistochemical methods combined with the retrograde transport of a protein gold complex we demonstrate that proNGF-like immunoreactivity is localized within neuronal cell bodies, in the cortex, hippocampus and septum. These results suggest that the immunological approach may not only identify NGF-synthesizing cells, but also cells which may accumulate proNGF or some cleavage products by an uptake mechanism.

Animals↗
PubMed1990

[Neuropathologic study of 50 cases of senile dementia].

Fifty brains from patients prospectively studied in a geriatric hospital (Charles Richet Study) were examined pathologically. The patients were senile (mean age: 85) and demented and had been clinically diagnosed as senile dementia of Alzheimer type (SDAT), vascular or multi-infarct dementia (VD), mixed dementia (MD). The whole brain was studied after formalin fixation and coronal sections. The senile changes were quantified in 6 neocortical areas, hippocampus and amygdala and subcortical structures after staining by thioflavine--S and Bodian's method. The other vascular and degenerative lesions were semiquantitatively studied. Three groups of patients were identified after microscopic examination: 1. SDAT (n = 27), 2. VD (n = 6), 3. MD (n = 15), 2 patients had no significant pathological correlate for dementia. Comparison of thioflavine S and Bodian's method in 30 cases showed the former to be more sensitive for the identification of senile plaques. In SDAT, 13/27 brains lacked neurofibrillary tangles in the neocortex. Amyloid angiopathy was observed in 78% of the brains but lacked in 5/6 cases affected by pure VD. Significant lesions of the substantia nigra were observed in 13 cases with typical features of Parkinson's disease in 2 cases. The locus coeruleus was affected mainly in SDAT cases (20/27) and in some cases of VD or MD (6/21). The raphe nuclei showed neuronal loss in 18% of the cases, mostly SDAT. In this series of cases, neocortical neurofibrillary tangles could be lacking in SDAT. Amyloid angiopathy was almost always present in SDAT and MD. Subcortical structures involved in cholinergic, noradrenergic and serotoninergic innervation of the cortex were more severely impaired in SDAT and MD than in VD. Mixed dementia was frequent in these very old demented patients. Clinical and pathological criteria are needed to identify this group of patients.

Aged↗
PubMed1990

[Effect of verapamil independent of its calcium channel antagonist action on hippocampal pyramidal neurons in rats].

The effects of verapamil, the phenylalkylamine calcium channel antagonist, have been studied on rat hippocampal pyramidal neurons, using intracellular recordings in an in vitro slice preparation. At low concentrations (1-10 microM), verapamil had no effect on these neurons. At higher concentrations (100-150 microM), it induced a progressive blockade of the slow component of the after-hyperpolarizing potential (AHP), but did not affect the fast one. Verapamil also blocked the slow inhibitory postsynaptic potential (sIPSP), but not the fast one. Pharmacological responses to the application of baclofen and serotonin were abolished, while the response to GABA was not. In addition, the size of the calcium spike was increased by verapamil, while the AHP and the sIPSP were already blocked. These results suggest that verapamil, applied at high concentrations, has an inhibitory effect on potassium conductances, independent of its calcium antagonist property.

Action Potentials↗
PubMed1989

Omega-conotoxin GVIA blocks synaptic transmission in the CA1 field of the hippocampus.

The effects of omega-conotoxin GVIA (omega-CgTx), a peptide isolated from the venom of a marine mollusc, were studied in rat hippocampal neurons. Intracellular recordings from the CA1 area were made for the purpose in in vitro slice preparations. Omega-CgTx (0.1-1 microM) rapidly and irreversibly blocked the EPSP and the IPSPs elicited by electrical stimulation of Schaffer collaterals/commissural fibers. Omega-CgTx also blocked the slow cholinergic EPSP induced by electrical stimulation of cholinergic afferents. The postsynaptic effects of baclofen or carbachol remained unchanged in the presence of omega-CgTx and other postsynaptic calcium-dependent events such as afterhyperpolarization were not affected by omega-CgTx. These results suggest a presynaptic action of omega-CgTx through the blockade of neurotransmitter release. Omega-CgTx might act in the hippocampus by blocking presynaptic N-type voltage-sensitive calcium channels.

Animals↗
PubMed1989

Age-related loss of galanin-immunoreactive cells in the rat septal area.

We have examined the distribution of galanin-like immunoreactive (LI) cell bodies in the medial septal nucleus (MS) and the nucleus of the diagonal band of Broca (nDBB) of young (3 months) and aged (25-30 months) rats, and assessed their respective contribution to the septohippocampal pathway. Immunohistochemical techniques were used alone or combined with the retrograde transport of a protein-gold complex injected into the dorsal hippocampus. In both groups, galanin-LI cells were observed in the MS and the nDBB. In aged rats, a significant decrease in both the staining intensity and the number of galanin-LI perikarya throughout the MS-nDBB complex was observed. Some immunoreactive cells appeared shrunken. The reduction in cell number ranged from 30 to 85%. There was also a decrease in the proportion of septohippocampal neurons containing galanin in aged rats (13% vs 20% in young animals) which however did not reach statistical significance. These results suggest that galanin-positive cells in the medial septal area undergo alterations with aging in the rat.

Aging↗
PubMed1989

Galanin blocks the slow cholinergic EPSP in CA1 pyramidal neurons from ventral hippocampus.

Using intracellular recordings from slice preparations, we studied the effects of the peptide galanin on the properties of CA1 pyramidal neurons from rat ventral hippocampus. Galanin, applied in the superfusing medium, had a weak and inconsistent effect on the membrane potential or on the afterhyperpolarization which follows a train of spikes. Galanin, which is localized in some cholinergic neurons of the septo-hippocampal pathway, did not affect the action of acetylcholine or carbachol on CA1 pyramidal neurons. However, it did have a presynaptic inhibitory effect on the cholinergic terminals, blocking the slow cholinergic excitatory post-synaptic potential (EPSP) induced by the release of endogenous acetylcholine on the pyramidal neurons. This effect was reversible and mimicked by atropine. These results suggest that the peptide galanin, colocalized with acetylcholine in some septo-hippocampal neurons might play a role in the control of acetylcholine release.

Animals↗
PubMed1989

Hemicholinium-3 selectively alters the rhythmically bursting activity of septo-hippocampal neurons in the rat.

The medial septal area contains neurons which project to the hippocampal formation. A sizeable proportion of these septo-hippocampal neurons (SHNs) are cholinergic. About 40% of them also display a characteristic discharge pattern in rhythmic bursts. We hypothesized that SHNs with a rhythmically bursting activity (RBA) are the cholinergic ones. To test this hypothesis we studied the effects of acetylcholine synthesis blockade by hemicholinium-3 (HC-3) on the properties of the SHNs. HC-3 (16, 32 or 64 micrograms total dose) or saline were injected in the lateral ventricles of adult male Sprague-Dawley rats anesthetized with urethane. Extracellular recordings from SHNs in the medial septal area were obtained within hours after HC-3 injections (n = 24 animals). SHNs were identified by their antidromic response following electrical stimulation of the fimbria-fornix. The pharmacological properties of SHNs were studied in some animals using microiontophoretic applications from multibarreled electrodes filled with various neurotransmitters. The hippocampal rhythmic slow activity (RSA or theta) was abolished even after the lowest dose of HC-3 tested (16 micrograms). No significant change in SHNs conduction velocity or spontaneous activity was observed at any dose of HC-3. The percentage of SHNs with RBA was unchanged. In contrast the mean frequency of the RBA was decreased by HC-3 in a dose-dependent fashion. The mean frequency was lowest within the first 3 h after injection. Although the mean spontaneous activity was unchanged SHNs tended to have more spikes per burst. The effects of various neurotransmitters on SHNs were qualitatively unchanged after HC-3 injection. These results suggest that acetylcholine synthesis blockade by HC-3 leads not only to the disappearance of the hippocampal RSA in urethane-anesthetized animals, but also to a decrease in the frequency of the rhythmically bursting activity of the SHNs. Since the 4-Hz hippocampal theta is atropine-sensitive, the results provide indirect evidence that the SHNs with rhythmically bursting activity are the cholinergic SHNs.

Action Potentials↗
PubMed1989

Rhythmical bursting activity and GABAergic mechanisms in the medial septum of normal and pertussis toxin-pretreated rats.

The possible involvement of GABA in the control of the rhythmical bursting activity (RBA) of septo-hippocampal neurons (SHNs) has been studied in the rat in vivo. The discharge frequency of SHNs was modified by the iontophoretic application of a GABA agonist and antagonist as well as by the application of the GABA uptake blocker, nipecotic acid. The GABAB agonist baclofen inhibited the SHNs' activity, this effect being antagonized by the GABAB antagonist phaclofen. However, these different pharmacological manipulations did not modify the RBA frequency. Pretreatment of the rats with pertussis toxin, a substance which is known to block the events mediated by G-proteins (Gi or Go), decreased the RBA frequency. Neither agonists nor antagonists of GABAA or GABAB types had significant effects on the rhythmical bursting activity of SHNs. The effect of pertussis toxin suggests that other neurotransmitters or intrinsic mechanisms involving a G-protein influence this rhythm.

Action Potentials↗
PubMed1989

Platelet [3H]-imipramine binding is not modified in Alzheimer's disease.

Platelet [3H]-imipramine binding was studied in patients with Alzheimer's disease and control subjects matched to the patients for age and sex. There were no differences in the binding parameters of [3H]-imipramine on platelet membranes from patients with Alzheimer's disease, when compared with the control group. These results suggest that [3H]-imipramine binding could be a useful tool to discriminate between demented and depressive patients in elderly populations.

Aged↗
PubMed1989

Cholinergic and peptidergic projections from the medial septum and the nucleus of the diagonal band of Broca to dorsal hippocampus, cingulate cortex and olfactory bulb: a combined wheatgerm agglutinin-apohorseradish peroxidase-gold immunohistochemical study.

We have examined the distribution pattern and the density of various neuropeptide, neurotransmitter and enzyme containing neurons in the rat medial septum and the nucleus of the diagonal band of Broca to assess their possible involvement in the septohippocampal, septocortical and septobulbar pathways. Immunohistochemical methods were combined with the retrograde transport of a protein-gold complex injected in the hippocampus, the cingulate cortex or the olfactory bulb. Cholinergic neurons were the most numerous. Galanin-positive neurons were about two or three times less numerous than cholinergic cells. Both these cell types had a similar location though the choline acetyl transferase-like immunoreactive cells extended more caudally in the horizontal limb of the nucleus of the diagonal band of Broca. Immunoreactive cells for other neuroactive substances were few (calcitonin gene-related peptide, luteinizing hormone releasing hormone. [Met]enkephalin-arg-gly-leu) or occasional (dynorphin B, vasoactive intestinal polypeptide, somatostatin, neurotensin, cholecystokinin, neuropeptide Y and substance P). No immunoreactive cells for bombesin, alpha atrial natriuretic factor, corticotropin releasing factor, 5-hydroxytryptamine, melanocyte stimulating hormone, oxytocin, prolactin, tyrosine hydroxylase or arg-vasopressin were present. Choline acetyltransferase- and galanin-like immunoreactive cells densely participate to septal efferents. Cholinergic neurons constituted the bulk of septal efferent neurons. Galanin-positive cells were 22% of septohippocampal, 8% of septocortical, and 9% of septobulbar neurons. Galanin containing septohippocampal neurons were found in the medial septum and the nucleus of the diagonal band of Broca; galanin-positive septobulbar and septocortical cells were limited to the nucleus of the diagonal band of Broca. Occasional double-labellings were noticed with some peptides other than galanin. Luteinizing hormone-releasing hormone, calcitonin gene-related peptide and enkephalin were the most often observed; some other projecting cells stained for vasoactive intestinal polypeptide or dynorphin B. Luteinizing hormone-releasing hormone, calcitonin gene-related peptide and enkephalin were observed in septohippocampal neurons; luteinizing hormone-releasing hormone and vasoactive intestinal peptide were observed in septocortical neurons and calcitonin gene-related peptide, luteinizing hormone-releasing hormone and dynorphin B were observed in septo-bulbar cells. These results show that, in addition to acetylcholine, galanin is a major cellular neuroactive substance in septal projections to the hippocampus, the cingulate cortex and the olfactory bulb. The presence of septal projecting neurons immunoreactive for other peptides shows that a variety of distinct peptides may also participate, but in a smaller number, to septal efferent pathways.

Animals↗
PubMed1989

Involvement of a pertussis toxin-sensitive G-protein in the pharmacological properties of septo-hippocampal neurones.

1. The physiological and pharmacological properties of identified septo-hippocampal neurones (SHNs) have been studied in rats pretreated with the bacterial toxin, pertussis toxin (PTX). 2. In rats anaesthetized with urethane and pretreated with PTX, the axonal conduction velocity was unchanged while the mean spontaneous activity was significantly increased. 3. PTX pretreatment had no effect on responses of SHNs to the iontophoretic application of gamma-aminobutyric acid (GABA) and cholinoceptor agonists (acetylcholine or carbachol). 4. Baclofen and 5-hydroxytryptamine (5-HT), almost exclusively inhibitory in control rats, had little effect or an excitatory effect in PTX pretreated rats. 5. These results suggest the involvement of a pertussis toxin-sensitive G-protein in responses medicated by 5-HT and GABAB-receptors but not in responses mediated by cholinoceptors and GABAA-receptors in medial septum neurones projecting into the hippocampus.

Animals↗
PubMed1988

Electrophysiological and pharmacological properties of neurons within solid basal forebrain transplants in the rat brain.

Electrophysiological and pharmacological properties of neurons within solid basal forebrain transplants were studied in adult rats anesthetized with urethane. No specific topography of the neurons recorded was observed within the graft. The mean spontaneous activity of the grafted neurons (GNs) was relatively low (4.9 impulses/s) but not unlike that of other central neurons in situ. A large proportion of GNs fired with regular discharges, but other modes of discharge were also observed. A few rhythmically bursting GNs were recorded having a discharge pattern very much like that of the rhythmically bursting medial septal neurons. The responses of GNs to glutamate, gamma-aminobutyric acid, acetylcholine, serotonin and norepinephrine was fairly similar to those described in other central structures.

Acetylcholine↗
PubMed1988

An electrophysiological laminar analysis of single somatosensory neurons in partially deafferented rat hindlimb granular cortex subsequent to transection of the sciatic nerve.

A sample of 302 neurons in rat hindlimb granular cortex was studied between 2 and 3 weeks after transection and ligation of the sciatic nerve. These neurons were compared to a control sample obtained from normal rats under similar experimental conditions. After sciatic nerve transection the proportion of neurons driven by somatic stimuli applied to the hindlimb (29.1%) was not significantly different from the proportion observed in the control sample (25.8%). The proportion of neurons with cutaneous receptive fields was also the same before and after nerve transection although the proportion of neurons responding to higher threshold taps was reduced. Spontaneously active neurons were encountered more frequently after sciatic nerve transection than in the control (45% vs 32%) and their mean discharge frequency was higher (8.6 vs 6.4 imp/s). Twice as many (10.2% vs 5.2%) spontaneously active neurons whose discharge was modulated by afferent stimuli were found after sciatic nerve transection. This and several other lines of evidence suggest that the cortical neurons were released from inhibition by the sciatic nerve transection. The number of spontaneously active neurons and the mean discharge rate were increased in each cortical lamina suggesting that the increased excitability seen after deafferentation occurred in all cortical layers. Neurons throughout the portion of the hindlimb representation studied could be driven from the remaining innervated region of the hindlimb, including one and sometimes two digits, part of the palm and most of the dorsum of the foot. More neurons were driven by receptive fields on the ankle than was the case for normal rats. Most neurons with cutaneous receptive fields were distributed in the same layers as those in the control group and had normal shapes and appearances. However, there were few of small size. Most were of moderate dimensions well within the normal range. Seven examples were found with unusually large proportions of their field extending from the foot onto the ankle and covering most of the posterior quadrant of the animal. In normal cortex the largest receptive fields were found in the middle layers. This distribution was not as clear after sciatic nerve section and a mixture of large and medium-sized receptive fields occurred at each depth. Further, some neurons with cutaneous receptive fields were found above 300 micron and below 1000 micron, depths where receptive fields were uncommon in the normal sample.

Action Potentials↗