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Y Lamour

Publications and source records attributed to Y Lamour.

At least 109 records · Page 6Linked to original sources
PubMed1983

A comparative study of two populations of acetylcholine-sensitive neurons in rat somatosensory cortex.

The properties of two populations of acetylcholine-sensitive neurons, defined by their different laminar distribution (group A, layers V and upper VIa; group B, layer VIb and underlying white matter) were studied in the SmI cortex of urethane-anesthetized rats. The spontaneous activity of group B neurons was significantly lower than in group A. The proportion of neurons excited by iontophoretic acetylcholine, the duration and the pharmacological properties of the excitations were the same in both groups. The dose-response curves obtained for sets of neurons of both groups, recorded with the same electrode, had comparable slopes. Carbachol had a greater potency than acetylcholine in both groups. In contrast, the latency of the response to acetylcholine was significantly shorter in group B. The amount of current required to increase the spontaneous discharge rate of a given neuron by 200% was lower in group B than in group A. These data suggest that the relative change in firing frequency induced by a given cholinergic input is likely to be larger in group B than in group A. Finally, neuronal excitations could still be obtained in both groups when acetylcholine was applied 300 micron, but not 600 micron, from the cell body, suggesting that the spatial distribution of acetylcholine receptors is similar in groups A and B.

Acetylcholine↗
PubMed1983

In vivo electrochemical detection of 5-hydroxyindoles in rat somatosensory cortex: effect of the stimulation of the serotonergic pathways in normal and pCPA-pretreated animals.

Differential pulse voltammetry was used for the detection of 5-hydroxyindoles in the cerebral cortex of rats anaesthetized with urethane. The stimulation of the lateral hypothalamus or of the dorsal raphe nucleus induced a 10-40% increase in the amplitude of the signal. The signal recorded from p-chlorophenylalanine (pCPA)-pretreated animals was much smaller than in normal animals and could be increased by 5-HTP administration. The stimulation of the serotonergic pathways was ineffective in the pCPA-pretreated animals.

Afferent Pathways↗
PubMed1983

Altered properties and laminar distribution of neuronal responses to peripheral stimulation in the SmI cortex of the arthritic rat.

The properties of the neuronal responses to different types of mechanical peripheral stimulation were studied during electrode penetrations in the first somatosensory cortex of anaesthetized rats with polyarthritis. Very few neurons were driven by light cutaneous stimulation (such as brushing) or by intense mechanical stimulation. Most of the neurons were driven by joint movement and/or moderate pressure on the skin. These neurons could be found in all cortical layers, the majority being located in layer V. These results contrast sharply with the properties and laminar distribution of the different functional categories of cortical neurons, as observed in normal animals.

Animals↗
PubMed1983

[Alzheimer's type dementia: recent data].

Dementia of the Alzheimer type (DTA) is the most common form of adult-onset dementia. The clinical features of the disease include progressive memory defect, intellectual impairment and behavioral disturbances. The number of patients suffering from DTA is increasing dramatically, due to the growing proportion of old people. DTA therefore is a major public health problem. Brain lesions include several histopathological changes (mostly in the cerebral cortex and hippocampus): neurofibrillary tangles, senile plaques, granulo-vacuolar degeneration, Hirano bodies, angiopathy, loss of nerve cells. Postmortem brain examination reveals characteristic neurochemical deficits. The most consistent reduction in neurotransmitter-synthesizing enzyme observed so far is a reduction in choline acetyltransferase activity, suggesting a cholinergic deficit. However, other deficits involving noradrenaline and somatostatin have also been reported. Several hypotheses (genetic, viral, toxic, immunologic, metabolic) have been put forward in order to explain DTA. The relationship between these hypotheses and the neurochemical deficits is still unclear, but the existence of characteristic neurotransmitter-related deficits allows specific therapeutic trials.

Aged↗
PubMed1983

Laminar distribution of serotonergic innervation in rat somatosensory cortex, as determined by in vivo electrochemical detection.

In vivo differential pulse voltammetry was used for the detection of indoleamines during vertical electrode penetrations in rat first somatosensory cortex, for studying the laminar distribution of serotonin and/or its metabolites in that part of the cortex. The peak of current corresponding to 5-hydroxyindoles was maximum in the most superficial part of the cortex and diminished gradually in the deeper layers. These results suggest that the cortical serotonergic innervation is predominant in the superficial layers.

5-Hydroxytryptophan↗
PubMed1983

Rat somatosensory (SmI) cortex: I. Characteristics of neuronal responses to noxious stimulation and comparison with responses to non-noxious stimulation.

Single unit responses to noxious and non-noxious somatic stimulation were investigated in the somatosensory (SmI) cortex of rats under halothane-nitrous oxide anaesthesia. Four categories of neurons were observed: (1) neurons driven by non-noxious cutaneous stimulation, (2) neurons driven by non-noxious deep stimulation, (3) neurons driven by noxious stimulation only (nociceptive specific neurons), (4) neurons driven by noxious as well as non-noxious stimulation (convergent or nociceptive non-specific neurons). The receptive fields of the neurons driven by contralateral cutaneous non-noxious stimulation were small. These neurons responded phasically to cutaneous stimulation in the majority of cases. Neurons driven by stimulation of deep receptors (e.g. joint movement) could also be recorded in the same part of SmI cortex. Neurons driven by noxious stimulation had large receptive fields and were often tonically driven by noxious stimulation. Convergent (or nociceptive non-specific) neurons could often be inhibited from body parts not included in their excitatory receptive field. Some neurons driven by noxious stimulation were able to encode stimulus parameters such as temperature of a hot water bath or surface of the skin area stimulated. The different categories of neurons defined above could be successively recorded during a given electrode penetration. Evidence for the somatotopic organization of the different categories of inputs was obtained. These results strongly suggest that the first somatosensory (SmI) neocortex is involved in nociception.

Afferent Pathways↗
PubMed1983

Effects of neuropeptides on rat cortical neurons: laminar distribution and interaction with the effect of acetylcholine.

The effects of the microiontophoretic application of five different peptides (cholecystokinin octapeptide sulfated form, cholecystokinin octapeptide non-sulfated form, vasoactive intestinal polypeptide, angiotensin-II and substance P) on cortical neurons were studied in rats anaesthetized with urethane. Vertical electrode penetrations were made in the first somatic sensory cortex and the laminar position of the neurons determined by the reconstruction of the tracks based on extracellular dye deposits. The first type of effect observed was an excitation of some cortical neurons. These neurons were mostly found in infragranular layers, specially in layer Vb. Pyramidal tract neurons were more often excited by peptides than the cortical population taken as a whole. Substance P excited the largest percentage of neurons, followed by vasoactive intestinal polypeptide and cholecystokinin octapeptide sulfated form, whereas angiotensin II and cholecystokinin octapeptide non-sulfated form were the least potent in terms of frequency of neurons excited as well as of amplitude of the responses. The vast majority of the neurons excited by a peptide could also be excited by acetylcholine. A second and independent effect of peptides was observed: the neuronal excitation induced by acetylcholine could be depressed by the simultaneous application of peptide. This depressing effect was also the most frequently observed with substance P, followed by cholecystokinin and vasoactive intestinal polypeptide.

Acetylcholine↗
PubMed1983

Somatosensory cortex activity related to position and force.

1. The relation of somatosensory cortex (SI) neuronal activity to actively maintained limb posture was examined by recording from single neurons in the SI of monkeys trained to hold the forearm at different pronation-supination postures and to exert different directions and magnitudes of steady torque. 2. Neurons related to limb position were, in most cases (89%), also related to torque exerted by the limb. Very few neurons related to only position or only torque were found. 3. Two categories of position- and torque-related neurons were found, type 1 and type 2. Type 1 eurneuronal activity resembled the pattern of activity seen in the pronator and supinator muscles; neurons more active with supinating torque also became more active with supinated position, while neurons related to pronating torque were also related to pronated position. Type 2 neurons had a noncongruent relation to position and torque; neurons more active with supinating torque became more active with pronated position, while neurons related to pronating torque were related to supinated position. 4. Position- and torque-related neurons were characterized by having predominantly noncutaneous peripheral inputs and were concentrated in two SI regions identified as area 3a and area 2. 5. It is hypothesized that during actively held limb postures, the activity of the type 1 and type 2 neuronal populations in SI is sufficient to signal uniquely the steady-state position of the limb and the force exerted by the limb.

Animals↗
PubMed1983

[Comparison of 2 groups of neurons sensitive to the excitatory effect of acetylcholine in the cerebral cortex of the rat].

Two groups of neurons which are excited by the iontophoretic application of acetylcholine were described in the primary somatosensory cortex of the Rat. The first one is located in the middle part (group A) and the second one in the deepest part of the cortex (group B). Group A neurons had a higher average spontaneous activity than group B neurons. The latency of group A neurons responses to the iontophoretic application of acetylcholine was longer. The amount of iontophoretic current required to increase the discharge rate of the neuron by 200% was higher in group A than in group B. In contrast the average slope of the regression lines calculated from dose-response curves was not different between the two groups.

Acetylcholine↗
PubMed1983

[Physiological and pharmacological properties of septohippocampal neurons identified by antidromic simulation in rats].

The physiological and pharmacological properties of septo-hippocampal neurons (identified through antidromic stimulation of the fimbria) were studied in the Rat under urethane anaesthesia. Half of these neurons (located in the medial septum and the nucleus of the diagonal band of Broca) displayed a rhythmic, bursting activity at about 4/s. A large majority of these neurons (bursting as well as non-bursting) could be excited through iontophoretic application of acetylcholine or carbachol.

Acetylcholine↗
PubMed1982

Topographic organization of basal forebrain neurons projecting to the rat cerebral cortex.

The topographic organization of basal forebrain neurons projecting to the rat cerebral cortex was investigated using the retrograde transport of horseradish peroxidase (HRP). HRP injections in cingulate and occipital cortices labeled neurons in the nucleus of the diagonal band of Broca. In contrast, injections in the frontal cortex labeled mostly neurons in the substantia innominata, and injections in the temporal and parietal cortices labeled neurons in the medial and ventral boundaries of the globus pallidus. These results suggest that the basal forebrain projection to the cerebral cortex is topographically organized.

Animals↗
PubMed1982

Spread of acetylcholine sensitivity in the neocortex following lesion of the nucleus basalis.

Neuronal responses to the iontophoretic application of acetylcholine, carbachol and nicotine were studied in rats, 2 or 3 weeks following bilateral lesions of the nucleus basalis region, and compared to those obtained in normal animals. The percentage of cortical neurons excited by acetylcholine and their individual sensitivity were higher in lesioned animals. Furthermore, the laminar distribution of the responses to acetylcholine and the proportion of responses to carbachol and nicotine were also modified.

Acetylcholine↗
PubMed1982

[Excitatory effects of 2 peptides on rat cortical neurons: laminar distribution and correlation with the effect of acetylcholine].

The most frequent effect observed following iontophoretic application of cholecystokinin or vasoactive intestinal polypeptide on Rat SI cortical neurons was an excitation. Most of the peptide-sensitive neurons were located in infragranular layers of the cortex. In most instances these neurons could also be excited by acetylcholine. These results suggest that some neuropeptides and acetylcholine might share common mechanisms of action on cortical neurons.

Acetylcholine↗
PubMed1982

[Physiologic and pharmacologic differences in 3 types of pyramidal cells identified by antidromic stimulation in the primary somatosensory cortex of the rat].

The physiological and pharmacological properties of three types of pyramidal neurons (pyramidal tract neurons, cortico-thalamic neurons and commissural neurons) identified by electrical antidromic stimulation were studied in the first somatic sensory cortex of the Rat. The laminar distribution of these neurons (as determined through histological reconstruction of the electrode tracks), their axonal conduction velocity, their sensitivity to iontophoretically applied acetylcholine and their ability to be driven by the stimulation of a peripheral somatic receptive field were shown to be different in the three groups. Some hypotheses are discussed, which could explain such differences.

Acetylcholine↗
PubMed1982

Neuronal responses to noxious stimulation in rat somatosensory cortex.

Neuronal responses to noxious stimulation applied on the skin of the limbs or of the tail were studied in the somatosensory cortex of rats under Fluothane/nitrous oxyde anesthesia. Among 694 neurons, 56 responded to noxious stimulation only and 35 to noxious as well as non-noxious stimulation. The receptive fields of these neurons were often larger than those of neurons recorded during the same penetration but unresponsive to noxious stimulation. They were able to encode stimulus parameters such as temperature of a hot water bath or size of the skin area stimulated. They were more frequently found in the deepest half of the cortex. These results suggest that the cerebral somatosensory cortex plays a role in pain mechanisms.

Action Potentials↗
PubMed1982

Excitatory effect of acetylcholine on different types of neurons in the first somatosensory neocortex of the rat: laminar distribution and pharmacological characteristics.

In rats anaesthetized with either urethane, pentobarbital or fluothane the effects of acetylcholine, cholinergic agonists and antagonists (applied by iontophoresis) were studied on single cortical neurons of first somatosensory region. The laminar distribution of the neurons excited by acetylcholine was determined by the reconstruction of each electrode track based on a dye-deposit made at the last recording site. Neurons were identified using antidromic stimulation of the pyramidal tract, the ventrobasal thalamus and the corpus callosum. Neurons excited by acetylcholine could be segregated into two groups: one encompassing layer Vb and the upper part of layer VI, the other more deeply located at the limit between the cerebral cortex and the subjacent white matter. Neuronal responses to glutamate and nicotine, unlike those to actylcholine were evenly distributed in the cortex. Pyramidal tract neurons had corticothalamic neurons were frequently excited by acetylcholine and were shown to be located with the first group of acetylcholine sensitive neurons. Commissural neurons were rarely excited by acetylcholine and were not restricted to either group. The analysis of neuronal responses to acetylcholine and various agonists (carbachol, nicotine, acetyl-beta-methylcholine, carbamyl-beta-methylcholine, butyrylcholine) and antagonists (atropine, mecamylamine) revealed a prominent but not exclusive muscarine character. It is included (i) that cortical neurons of first somatosensory cortex which are excited by acetylcholine belong to two populations, one consisting, at least in part, of projection neurons (upper group) and the other of interneurons (lower group); (ii) that cortical acetylcholine receptors are of a 'mixed' type strongly weighted toward the muscarinic side.

Acetylcholine↗
PubMed1982

Laminar distribution and convergence of deep and superficial peripheral inputs in the forelimb representation of rat SI somatosensory cortex.

The laminar distribution of single unit responses to stimulation of peripheral nerves (deep and superficial radial nerves) or to stimulation of peripheral receptive fields has been studied in the forelimb representation of the first somatic sensory cortex (SI) of the rat. 1. Under both conditions the majority of the responding units was located in layers IV, V and VI of the cortical area containing dense neuronal aggregates in layer IV. 2. Following electrical stimulation of the deep radial nerve (DRN) and of the superficial radial nerve (SRN), 18.9% of the neurons were observed to receive convergent inputs from both nerves. 3. Following natural stimulation of the forelimb, no evidence of convergent inputs on single neurons was obtained. 4. There was no clear submodality segregation in the receptive fields observed during vertical penetration.

Animals↗