Biomedical subjects

P Dutar

Publications and source records attributed to P Dutar.

At least 73 records · Page 4Linked to original sources

PubMed1985

Activation of identified septo-hippocampal neurons by noxious peripheral stimulation.

Septo-hippocampal neurons (SHNs) were recorded from the medial septum-diagonal band area of rats anaesthetized with either urethane or fluothane. They were identified by their antidromic response to the electrical stimulation of the fimbria. Their responses to peripheral somatic noxious and non-noxious stimulation were studied. Non-noxious natural stimulations were relatively ineffective. In contrast, 68% of the SHNs were driven by noxious stimulation. The SHNs could be driven either by mechanical or thermal stimulation. Intraperitoneal injection of bradykinin excited about half of the SHNs. Some neurons were able to encode stimulus intensity (strength of the mechanical stimulation and/or temperature of the thermal stimulation). The receptive fields of the SHNs were large, usually involving half of the body or the whole body surface. These results suggest that SHNs, which are at the origin of the cholinergic septo-hippocampal pathway, might be involved in cerebral mechanisms related to nociception.

Animals↗

PubMed1985

Cerebral neocortical neurons in the aged rat: spontaneous activity, properties of pyramidal tract neurons and effect of acetylcholine and cholinergic drugs.

The properties of cortical cerebral neurons have been studied and compared in 2, 22 and 26 month-old Sprague-Dawley rats, using electrophysiological techniques. The mean spontaneous activity of the neurons in old animals (unidentified as well as pyramidal tract neurons) was not different from that of young adult rats. In contrast the mean latency of the antidromic response of pyramidal tract neurons to pyramidal tract stimulation was significantly longer in 26 month-old animals. No difference was observed in the effects of the excitatory amino acid glutamate applied by iontophoresis. The percentage of cortical neurons excited by the iontophoretic application of acetylcholine was similar in young and old animals. Neither the laminar distribution, nor the individual sensitivity of these neurons to acetylcholine were found to be modified. The pharmacological properties of the acetylcholine-induced excitations were unchanged, exhibiting muscarinic as well as nicotinic properties. These results are consistent with the suggestion that the impairment of the cholinergic system with aging is for a large part presynaptic. They also emphasize the fact that several physiological and pharmacological properties of the cerebral cortical neurons show little change with age in Sprague-Dawley rats.

Acetylcholine↗

PubMed1985

[Properties of thalamocortical cells identified by antidromic stimulation in the ventrolateral and ventrobasal thalamic nuclei in rats].

The physiological and pharmacological properties of thalamocortical neurons, identified by electrical antidromic stimulation of the frontoparietal cortex, were studied in the ventrobasal and ventrolateral thalamic nuclei in urethane anaesthetized rats. The spontaneous activity and conduction velocity of these neurons were similar in both nuclei. At both sites, thalamocortical neurons could be excited through iontophoretic application of acetylcholine and muscarinic or nicotinic agonists. Despite the known differences in thalamic organization of the two species, these properties are quite similar to those described in cat by other authors.

Acetylcholine↗

PubMed1984

Septo-hippocampal and other medial septum-diagonal band neurons: electrophysiological and pharmacological properties.

Neurons located in the medial septum-nucleus of the diagonal band (vertical limb) area and antidromically activated by electrical stimulation of the fimbria were recorded in urethane anesthetized rats. Forty-five percent of these septo-hippocampal neurons (SHNs) discharged rhythmically in short bursts (mean burst frequency, 4 Hz). They were antidromically driven at short latencies from the fimbria. SHNs driven at long latencies (above 5 ms) were never bursting neurons. Fimbria stimulation also had a powerful inhibitory effect on the spontaneous activity of SHNs. The vast majority of the septo-hippocampal neurons were excited by the iontophoretic application of acetylcholine or cholinergic agonists, carbachol being the most effective. The acetylcholine-induced excitations were readily abolished by atropine. In contrast hexamethonium and mecamylamine were less effective. The rhythmic bursting activity could not be consistently altered by the iontophoretic application of cholinergic agonists or antagonists or of divalent cations. SHNs were also sensitive to various other putative neurotransmitters (substance P, GABA) known to play a role in the medial septal area. Bursting neurons and ACh-sensitive neurons were less frequent among unidentified medial septal neurons. The regulation of the septo-hippocampal cholinergic pathway is therefore not likely to be due to a direct feedback inhibition by locally released acetylcholine. However a strong inhibitory feedback could be exerted by the hippocampo-septal pathway impinging directly or indirectly on septo-hippocampal neurons.

Animals↗

PubMed1984

Cortical projections of the nucleus of the diagonal band of Broca and of the substantia innominata in the rat: an anatomical study using the anterograde transport of a conjugate of wheat germ agglutinin and horseradish peroxidase.

The projections of the nucleus of the diagonal band of Broca and of the substantia innominata to the cerebral cortex were studied in the rat, using the anterograde transport of wheat germ agglutinin conjugated with horseradish peroxidase. Following diagonal band injections, fibers were observed ascending in the septum and reaching the cingulate cortex. They had a rostrocaudal, horizontal direction, mostly in layer VI and could be followed over long distances on sagittal sections. The fibers gave off collaterals which were seen ascending in the cerebral cortex and reaching more superficial layers. Following substantia innominata injections, fibers were observed to take two routes: the first one identical to the one described above and a second through the caudate-putamen reaching the temporo-insular cortex. Terminal fields had a more diffuse distribution following substantia innominata than following diagonal band injections. No clear laminar pattern of termination was observed. However the density of terminals was higher in layers IV, V and VI than in layers I, II and III. Since the conjugate used is not taken up by fibers of passage, this pattern of connection is believed to reflect the organization of the projection of the nucleus of the diagonal band and of the substantia innominata to the cerebral cortex.

Animals↗

PubMed1983

Acetylcholine excites identified septo-hippocampal neurons in the rat.

Neurons of the medial septum-nucleus of the diagonal band of Broca (vertical limb) area were identified as septo-hippocampal neurons by antidromic electrical activation in anesthetized rats. A large majority of these presumably cholinergic neurons could be excited by the iontophoretic application of acetylcholine or cholinergic agonists such as carbachol. The acetylcholine-induced excitations were readily antagonized by atropine. These results suggest that cholinergic neurons can be excited by their own transmitter, i.e. acetylcholine.

Acetylcholine↗

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

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

[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

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↗

PubMed1981

[Laminar distribution of excitatory responses to acetylcholine in rat somatic sensory cortex: a microionophoretic study].

The laminar distribution of excitatory responses to iontophoretically applied acetylcholine (ACh) was studied in the first somatic sensory cortex (SI) of the Rat, using extracellular dye deposits for reconstruction of the electrode tracks. Most of the responses were recorded from neurons located in the lower half of the cortex, namely in layers V and VI. ACh sensitive neurons were found in two locations: one encompassing layer V and upper part of VI and the other at the border between cortex and white matter. The functional significance of this distribution is discussed.

Acetylcholine↗

PubMedDate not supplied

Neuropeptides and septo-hippocampal neurons: electrophysiological effects and distributions of immunoreactivity.

The septo-hippocampal neurons (SHNs), located in the medial septum, project to the hippocampal formation. The population of SHNs, as shown by single unit recordings in urethane-anesthetized rats, is heterogeneous, both in terms of patterns of spontaneous activity (a significant proportion of the SHNs display a characteristic rhythmically bursting activity at about 4 Hz) and of conduction velocity. Their average rate of spontaneous discharge is quite high (20 impulses per second). They are excited by the iontophoretic application of acetylcholine and various cholinergic agonists. They are also excited by some peptides such as substance P and TRH. Parallel studies in aged animals show that the physiological properties of the SHNs are altered, while their pharmacological properties seem to be unchanged. Immunohistochemical investigations using antibodies against various peptides and a monoclonal antibody against choline acetyltransferase (ChAT) show that SHNs retrogradely-labeled from the hippocampus often contain ChAT, less frequently galanin-like immunoreactivity and in a few cases enkephalin, luteinizing hormone-releasing hormone, or calcitonin gene-related peptide. In contrast, cholecystokinin, vasoactive intestinal peptide, substance P, somatostatin, dynorphin-B and neurotensin, although present in some medial septal neurons, were never observed in neurons projecting to the hippocampus.

Acetylcholine↗

PubMedDate not supplied

Age-related alterations in the properties of hippocampal pyramidal neurons among rat strains.

We compared age-related alterations in the electrophysiological and pharmacological properties of CA1 hippocampal pyramidal neurons in three strains of rats (Sprague-Dawley, Fisher 344, and Wistar) at 3-4 and 25-32 months of age, using the in vitro slice preparation. The most consistent age-related alterations in the properties of rat hippocampal neurons were: a decrease in membrane excitability, a decrease in the amplitude and duration of inhibitory postsynaptic potentials and a decreased sensitivity to the effect of the cholinergic agonist carbachol. In contrast, no consistent alterations in calcium-dependent events were observed in these strains of rats. The age-related changes in the duration of the afterhyperpolarizations (AHPs) were different (and even opposite) depending on the strain studied. Our results show that age-related changes observed in a given strain are not necessarily present in all strains of the same species.

Aging↗