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A Privat

Publications and source records attributed to A Privat.

At least 145 records · Page 8Linked to original sources
PubMed1992

Plasticity of the serotonergic innervation of the dorsal horn of the rat spinal cord following neonatal capsaicin treatment.

Neonatal capsaicin treatments (25 or 50 mg/kg, 12, 24, or 48 hr after birth given subcutaneously) were applied in order to follow by immunocytochemical techniques the postnatal development and plasticity of the serotonergic system in the dorsal horn of the rat spinal cord. Two markers of the lesions of C primary afferents induced by capsaicin were tested by immunocytochemical detection: substance P and calcitonin gene-related peptide (CGRP). We show that the internal part of substantia gelatinosa (lamina Ili) which does not contain serotonergic fibers in intact or vehicle-treated rats is invaded within a few days after capsaicin treatment by serotonergic fibers apparently sprouting from the deepest laminae. Moreover, these fibers often establish axodendritic synapses while synapses are rare in intact animals in the whole dorsal horn. This reorganization is stable whatever the dose of capsaicin used or the moment chosen for its injection. On the other hand, while lesions of substance P-ergic fibers appeared quite stable, partial recovery of CGRP innervation was found after 3 to 6 months, especially with the low dose of capsaicin. We discuss the ability of the serotonergic system innervating the dorsal cord either to find new targets or to fill vacated sites when one of its putative targets is removed.

Aging↗
PubMed1992

Effects of neonatal removal of superior cervical ganglion on serotonin and thyrotropin-releasing hormone immunoreactivity in the intermediolateral cell column of the rat spinal cord.

In this study, we investigated the effects of the neonatal removal of the right superior cervical ganglion on the serotonin-like and thyrotropin-releasing-hormone-like immunoreactivities (5-HT-LI and TRH-LI) in the intermediolateral cell column (IML) of the spinal cord by quantitative image analysis. Two weeks after the lesion, we observed a 60% reduction in 5-HT-LI, while TRH-LI was not significantly reduced, in the right IML (lesioned side) at T1-2 levels. One month after the lesion, 5-HT-LI and TRH-LI were significantly reduced by 60% in the right IML at T1-2 levels. After 3 months, this decrease persisted at this level. In addition, we observed a 30% loss of the 5-HT-LI in the right IML at T3-4 levels, whereas TRH-LI did not decrease significantly at T3-4 levels. These findings are discussed and compared with those of other experimental studies on serotonergic reorganization in the rat spinal cord.

Aging↗
PubMed1992

Immunocytochemical mapping of noradrenergic projections to the rat spinal cord with an antiserum against noradrenaline.

The mapping of noradrenergic innervation was performed in transverse and longitudinal sections of the adult rat spinal cord using noradrenaline immunocytochemistry. Noradrenergic fibres and terminals were distributed in the dorsal horn (mainly in the superficial part), in the vicinity of the different groups of motoneurons, and concentrated in the intermediolateral cell column and around the central canal. The ultrastructural study showed principally axodendritic synapses in the ventral horn and in the intermediolateral cell column. Fewer axosomatic synapses were detected. In the dorsal horn, noradrenaline-innervation was predominantly non-synaptic. It is hypothesized that the noradrenergic modulation of nociception is not mediated through classical synapses. The concept of 'volume transmission' can explain such an influence. Conversely, noradrenaline may be involved in the control of locomotion and automatic functions through conventional synapses.

Animals↗
PubMed1992

Distribution of thyrotropin-releasing hormone in the rat spinal cord with special reference to sympathetic nuclei: a light- and electron-microscopic immunocytochemical study.

This paper deals with the distribution of thyrotropin-releasing hormone-like immunoreactivity in the spinal cord of the rat, and particularly in the sympathetic nuclei, at light and electron microscopic levels. In the dorsal horn, the inner part of laminae II and III displayed thin thyrotropin-releasing hormone immunoreactive profiles. Electron microscopy revealed small immunoreactive varicosities which made synaptic contact with small dendrites or dendritic spines. Dense thyrotropin-releasing hormone-like immunoreactivity was observed in all sympathetic nuclei (nucleus intermediolateralis pars fascicularis and principalis, nucleus intercalatus and dorsal commissural nucleus) except the nucleus intercalatus pars ependymalis. Electron microscopy showed many immunoreactive varicosities which were often in synaptic contact with dendrites (proximal or distal), rarely with perikarya and never with axons. Sometimes, the same immunoreactive varicosity made axodendritic contacts with two dendrites and, conversely one dendrite was sometimes synaptically contacted by two or more immunoreactive varicosities. The ventral horn displayed a diffuse thyrotropin-releasing hormone-like immunoreactivity except for the cremaster nucleus (at lumbar level) which was densely outlined by immunoreactive profiles. Occasionally a large cell body in lamina IX (a putative motoneuron) was outlined by immunoreactive profiles but ultrastructural studies revealed very few immunoreactive axosomatic synapses, while immunoreactive symmetrical or asymmetrical axodendritic synapses were observed. The present study clearly confirms the existence of thyrotropin-releasing hormone immunoreactive synapses, thus substantiating the physiological role of this hormone in the spinal cord.

Animals↗
PubMed1992

Fate of B1-B2 and B3 rhombencephalic cells transplanted into the transected spinal cord of adult rats: light and electron microscopic studies.

Embryonic cell suspensions (14-day embryos) containing either B3 or B1-B2 serotonergic cell groups were obtained by microdissection of specific rhombencephalic regions and transplanted into the transected spinal cord of adult male Sprague-Dawley rats. After 3 months of survival, the animals were sacrificed and the spinal cords processed for the immunocytochemical detection of serotonin (5-HT). 5-HT-immunoreactive fibers from B1-B2-grafted cells were selectively distributed in the ventral horn and the intermediolateral cell column (IML) where they established conventional synaptic contacts. However, B3 5-HT cells grew and extended their processes into the dorsal horn where in addition we observed scarce synaptic contacts as in the normal spinal cord. These results suggest that the specificity of the 5-HT innervation of the spinal cord by grafted neurons is due, at least partly, to the presence of local mechanisms mediating guidance and cell recognition, possibly operating in conjunction with preexisting substrate pathways.

Animals↗
PubMed1992

7 beta-hydroxycholesterol and 7 beta-hydroxycholesteryl-3-esters reduce the extent of reactive gliosis caused by an electrolytic lesion in rat brain.

Electrolytic lesions performed in brain cortex of six-day-old or adult rats resulted in the appearance of many reactive astrocytes around the injury site after a postoperative delay of eight days. They were revealed by immunohistochemistry using antibodies against glial fibrillary acidic protein. Injection of tritiated thymidine 24 h prior to autopsy indicated that, in neonates, 50% of the reactive astrocytes were proliferating. Infusion of 2 microliters of liposome suspension made of phosphatidylcholine and a monosialoganglioside, in the injury site, immediately after the electrolytic lesion did not modify the extent of the reactive gliosis. Liposomes containing 3 nmol of either 7 beta-hydroxycholesterol, 7 beta-hydroxycholesteryl-3-stearate or 7 beta-hydroxycholesteryl-3-oleate reduced by about 50% the intensity of the reactive gliosis in the frontal cortex of six-day-old rats and by 40% the number of dividing astrocytes. In the adult rat cortex the intensity of the glial reaction was also decreased by 30% by 15 nmol 7 beta-hydroxycholesteryl-3-oleate. Further investigations demonstrated that it is the 7 beta-hydroxy function which is needed for the biological activity of these oxysterols. These findings, which demonstrate anti-proliferative and anti-inflammatory properties of 7 beta-hydroxycholesterol on astrocytes, facilitate the future investigation of the influence of reactive gliosis on functional recovery following brain injury. This anti-proliferative property could also be used in other kinds of pathologies involving glial cell proliferation, such as glioblastomas.

Animals↗
PubMed1991

Localization of dopamine carriers by BTCP, a dopamine uptake inhibitor, on nigral cells cultured in vitro.

BTCP, N-[1-(2-benzo(b)thiopenyl)cyclohexyl]piperidine, a derivative of phencyclidine, acted as a potent dopamine (DA) uptake blocking agent on primary cultures of dopaminergic neurons obtained from substantia nigra (IC50 = 70 nM). This value was closely related to IC50 determined for reference DA uptake inhibitors such as nomifensine (70 nM) or benztropine (50 nM), showing the specificity of BTCP towards the DA carrier. Thus, we used BTCP as a tool to visualize the DA uptake complexes on cultures, a model which preserves the integrity of the neurons. The [3H]BTCP binding sites directly visualized by radioautographical (RAG) labelling seemed to follow the fibres (axons or dendrites) of neurons in culture whereas the cell bodies were not labelled. The [3H]DA uptake visualized by RAG labelling, was inhibited either partially by BTCP at a concentration near its IC50 or totally by a high concentration of BTCP, all over the dopaminergic neurons (neurites and somas) immunostained with an anti-DA antiserum. Thus, the distribution of DA carriers can be investigated by a suitable tool, BTCP, a powerful and selective DA uptake blocker. These carriers have been visualized by radioautography with tritiated BTCP along the neurites, and the uptake can be totally blocked by a high concentration of BTCP all over DA neurons in vitro.

Animals↗
PubMed1991

Modification of serotonergic immunoreactive pattern in the dorsal horn of the rat spinal cord following dorsal root rhizotomy.

We investigated by immunocytochemistry the reorganisation of serotonergic endings in the dorsal horn of the rat spinal cord following thoracolumbar unilateral rhizotomy. The extent of the removal of primary afferent fibres was testified 2 weeks and 4 months after surgery by the disappearance of almost all calcitonin gene-related peptide (CGRP) immunoreactivity in the dorsal horn. Two weeks after surgery, serotonin immunoreactivity was severely reduced within the whole dorsal horn. Then, after 4 months, we observed a regrowth of serotonergic axons giving rise to an immunoreactive pattern close to that of intact animals, except in lamina IIi which was spanned by growing fibres. Thus, the removal of putative targets of serotonergic axons in the dorsal horn induces a transient loss of immunoreactivity, which illustrates the interaction between primary afferents and descending bulbo-spinal fibres.

Animals↗
PubMed1991

Autoradiographic mapping of 5-HT1, 5-HT1A, 5-HT1B and 5-HT2 receptors in the rat spinal cord.

The distribution of 5-HT1, 5-HT1A, 5-HT1B and 5-HT2 receptors in the rat spinal cord was investigated with quantitative autoradiography. Receptors were labeled respectively with [3H]serotonin (5-[3H]HT),8- hydroxy-2-[N-dipropylamino-3H]tetralin (8-OH-[3H]DPAT), [125I]iodocyanopindolol and [3H]ketanserin. It is shown that 5-HT1, 5-HT1A and 5-HT1B receptors are distributed within the spinal cord according to a rostro-caudal gradient. Both 5-HT1 and 5-HT1A receptors are mainly present in the dorsal horn and 5-HT1B is present throughout the spinal cord, exhibiting high densities in the caudal-most part of the dorsal horn in lamina X and in the sacral parasympathetic area. On the other hand, 5-HT2 receptors are shown mostly in the thoracic sympathetic area and in the thoracic ventral horn; the dorsal horn exhibits few 5-HT2 receptors. The differential involvement of 5-HT through different receptors in nociception, autonomous nervous system control and motility are discussed.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1991

Electronmicroscopic detection of the axonal coexistence of serotonin and substance P in B1-B2 raphé cells transplanted into the transected spinal cord of adult rats.

One week after a complete spinal cord transection at the thoracic (T8) level in adult rats, a suspension of rhombencephalic embryonic (day 14) cells containing the B1-B2 serotonergic groups was injected below the section. After a survival period of one month, the spinal cord was processed for an ultrastructural dual immunocytochemical detection of serotonin (5-HT) and substance P (SP). It was shown by ultrastructural dual immunolabeling that 5-HT and SP coexist in the same axon terminals of transplanted cells.

Animals↗
PubMed1991

Non-competitive antagonists of N-methyl-D-aspartate prevent spontaneous neuronal death in primary cultures of embryonic rat cortex.

Primary cultures of embryonic rat cerebral cortex were treated after 17 days in vitro for 10 min with a single dose of the non-competitive antagonists of N-methyl-D-aspartate (NMDA) receptor MK 801, TCP, and GK 11. They were then maintained in vitro for 31, 59, or 73 days, and then processed for the immunocytochemical detection of neuron-specific enolase (NSE). Immunoreactive cells were counted in treated and control cultures, and it was found that, except at 31 days, treated cultures contained far more NSE immunoreactive cells than controls. Moreover, this effect was dose-dependent, since with both TCP and GK 11 neuron survival was significantly higher with, respectively, 20 microM and 5 microM than with the lowest concentration of 2.5 microM. We tentatively conclude that spontaneous neuron death occurring in primary cultures in vitro is at least partly related to the NMDA-associated Ca++ channel, since the common property of the molecules we used is to block this channel. The relevance of this mechanism of cell death in vitro to neuronal death in vivo is discussed.

Animals↗
PubMed1991

Immunohistochemical evidence for the coexistence of substance P, thyrotropin-releasing hormone, GABA, methionine-enkephalin, and leucin-enkephalin in the serotonergic neurons of the caudal raphe nuclei: a dual labeling in the rat.

By means of dual immunohistochemical labeling on the same brain section examined with a light microscope, the present study reports the presence with serotonin (5-hydroxytryptamine; 5-HT) of gamma-aminobutyric acid (GABA), substance P (SP), thyrotropin-releasing hormone (TRH), leucin-enkephalin (LEU-enk), or methionine-enkephalin (MET-enk), within the same neuron in the nuclei raphe magnus, raphe obscurus, and raphe pallidus of the rat. On the one hand, peptides or GABA are detected with specific rabbit antibodies by indirect peroxidase labeling using peroxidase-conjugated Fab fragments, and on the other, 5-HT is detected with a rabbit antibody against the BSA-serotonin conjugate by radio-immunocytochemistry using [125I]-labeled protein A. The possible coexistence of TRH and SP in these neurons is also investigated by using peroxidase labeling and radio-immunocytochemical detection, respectively. In the whole caudal raphe nuclei the proportion of each coexisting peptide with 5-HT appears in decreasing order as: TRH greater than SP greater than MET-enk # LEU-enk greater than GABA. In all instances the level of coexistence differs considerably in B1-B2 vs. B3 cell groups. No SP/TRH dually labeled cells have ever been found in any of the serotonergic nuclei of the caudal raphe. Given the evidence that these raphe nuclei project possibly to the spinal cord, these data constitute an anatomical substrate for the several distinct physiological functions presumably subserved by 5-HT in the cord, namely the modulation of nociception, motor, and autonomic functions.

Animals↗
PubMed1991

Modifications of serotonin-, substance P- and calcitonin gene-related peptide-like immunoreactivities in the dorsal horn of the spinal cord of arthritic rats: a quantitative immunocytochemical study.

Adjuvant-induced arthritis has been produced in adult rats in order to study the reorganization of serotonergic innervation in the spinal cord dorsal horn in a model of chronic pain. Immunocytochemical detection of CGRP and substance P was quantified with an image analyzer, and we found a transient increase for both peptides at 1 and 2 months, followed by a decrease to control levels after four months. At variance, quantification of serotonergic immunoreactivity showed a significant increase which persisted throughout the study. The significance of this finding is discussed with comparison of other experimental models involving reorganization of primary afferents to the spinal cord.

Animals↗
PubMed1991

Serotonergic innervation of the dorsal horn of rat spinal cord: light and electron microscopic immunocytochemical study.

The ultrastructure of serotonergic projections to the dorsal horn of the rat spinal cord has been investigated, using a highly specific polyclonal antiserum. The highest concentrations of immunoreactive profiles were found in lamina I and the outer part of lamina II (IIo). Intermediate concentrations were found in laminae III and IV, while the inner part of lamina II (IIi) was almost devoid of immunoreactivity. Whereas 60% of the profiles show at least one varicosity studded with synaptic vesicles, only one-fifth of the latter contributes to classical synapses, the remaining profiles being devoid of a facing postsynaptic density. The results are compared with those in the literature and our own results relative to other regions of the cord. It is concluded that the pauci-synaptic projections to the dorsal horn could correspond to a diffuse influence of serotonin, the targets for which are determined by the corresponding serotonergic receptors.

Animals↗
PubMed1990

Transplantation of serotonergic neurons into the 5,7-DHT-lesioned rat olfactory bulb restores the parameters of kindling.

In order to restore a normal pattern of kindling, kindled rats, previously lesioned in the olfactory nuclei with 5,7-dihydroxytryptamine, were grafted with serotonin (5-HT) neurons in the right olfactory bulb and then implanted for kindling procedure. It was observed that complete 5-HT lesions accelerated the kindling profile, and that the transplants containing 5-HT neurons restored, in lesioned rats, quite normal parameters.

5,7-Dihydroxytryptamine↗
PubMed1990

Modification of serotonergic innervation of the rat spinal cord dorsal horn after neonatal capsaicin treatment.

Newborn rats were treated with Capsaicin. Seven weeks later, calcitonin gene-related peptide, substance P, and serotonin were detected immunocytochemically in the dorsal horn of the spinal cord. Peptide immunostaining, presumably located in primary afferents, was reduced in intensity, whereas the pattern of serotonin innervation was modified, suggesting a secondary reorganization due to the lesion of afferents. The possible mechanisms of this reorganization are discussed.

Animals↗
PubMed1990

Calcitonin gene-related peptide staining intensity is reduced in rat lumbar motoneurons after spinal cord transection: a quantitative immunocytochemical study.

The expression of Calcitonin gene-related peptide (CGRP) has been demonstrated in motoneurons of several species. We have investigated in adult rats the influence of transection of the spinal cord on CGRP immunoreactivity of motoneurons located below the section. Quantitative analysis has been performed with computer-assisted image analysis. As early as 48 h after the section, CGRP immunoreactivity is modified, and the reduction is maximal after one month. Then, both the number of immunoreactive cells and the intensity of staining increase until the 5th month. It is concluded that the expression of CGRP is under the influence of supraspinal afferents to the motoneuron.

Animals↗