RésuméLes interactions entre le système nerveux central et le système immunitaire ainsi que le rô... more RésuméLes interactions entre le système nerveux central et le système immunitaire ainsi que le rôle important des neurotransmetteurs et des cytokines dans cette communication bidirectionnelle sont aujourd’hui bien admis. Les deux systèmes synthétisent de surcroît certains médiateurs communs, telles les endomorphines dérivées de la proopiomélanocortine et de la proenképhaline A. Les résultats obtenus aussi bien chez l’animal in vivo que dans des expériencesin vitro suggèrent que les opioïdes (exogènes et endogènes) sont doués d’effets immunomodulateurs. L’action immunomodulatrice des morphiniques pourrait être indirecte, par le biais de récepteurs des opioïdes centraux, dont la sollicitation met en jeu des voies de signalisation qui ne sont que partiellement identifiées (axe hypothalamohypophysaire, système nerveux sympathique …), et directe, via les récepteurs des opioïdes des cellules immunocompétentes. La signification réelle des interactions entre opioïdes et système immunitaire n’est pas établie. Les travaux effectués chez l’homme n’apportent pas de réponse à cette question cruciale. De fait, force est de constater que peu d’études fiables (faible nombre de sujets, notamment…) ont été réalisées chez l’homme, et moins encore chez des patients douloureux traités de façon prolongée avec des morphiniques. Néanmoins, malgré leurs insuffisances, les données disponibles n’indiquent pas que les morphiniques au long cours aient des effets immunosuppresseurs majeurs, que ce soit chez des sujets exempts de douleur ou douloureux. Cette constatation peut être rapprochée du fait qu’aucune étude d’ordre épidémiologique n’a pu établir un lien entre toxicomanie aux opiacés et diminution du taux des cellules T CD4+ chez des patients séropositifs pour le VIH. Certains auteurs émettent d’ailleurs l’hypothèse générale que les opioïdes joueraient le rôle d’un frein homéostatique du système immunitaire qui permettrait en réalité à ce dernier d’être plus réactif lors d’une nouvelle agression. Ainsi, les données actuelles ne constituent pas un fort niveau de preuve en faveur d’effets délétères des morphiniques sur les défenses immunitaires des patients.SummaryThe existence of close interactions between central nervous and immune systems, as well as the preponderant action of neurotransmitters and cytokines in this cross-talk are well documented. In addition, both systems are endowed with several common mediators such as proopiomelanocortin-and proenkephalin A-derived opioid peptides. The immunomodulatory effects of opioids are supported by numerousin vivo andin vitro experimental data. This modulation could be elicited indirectly, via central opioid receptors stimulation and subsequent activation of different, only partially identified, pathways (hypothalamic-pituitary-adrenal axis, sympathetic innervation), or directly through the stimulation of opioid receptors located on immunocompetent cells.However, the physiological impact of this relationship is still unclear and available data from clinical trials do not supply an unequivocal answer. In fact, only few studies were carried out, most of those on healthy subjects and additional few on patients suffering from chronic painful conditions that were on long-term morphine treatment. Nevertheless, the data reported so far are not in favor of a major impact of prolonged opiates treatment on immune response either in subjects without pain or in patients suffering from painful conditions. It can be also pointed out that no epidemiological data exist to support some relation between opiates abuse and CD4+ T cells decreased levels in HIV positive patients. Several authors hypothesized that following the immune system activation, opioids might act as homeostatic regulators of immune system, thus increasing the reactivity and appropriate responses of the system to a novel aggression. Taking together, the available clinical data do not clearly evidence the existence of some deleterious effect of opiates on patients immune defense.
Calcitonin gene-related peptide (CGRP) in the dorsal horn of the rat spinal cord was assumed unti... more Calcitonin gene-related peptide (CGRP) in the dorsal horn of the rat spinal cord was assumed until now to be principally of primary afferent origin. It is shown here, on the basis of both light and electron microscopic immunocytochemical evidence, that some cell bodies of the dorsal horn and lateral spinal nucleus (LSn) of the rat cervical spinal cord contain a CGRP-like immunoreactivity. At the light microscopic level, immunoreactive cell bodies were observed in animals pretreated with colchicine injected intraventricularly, CGRP-like cell bodies were morphologically heterogeneous and distributed in the three superficial layers of the dorsal horn. They were very rare in lamina I and more numerous in laminae II and III. A group of immunoreactive cell bodies was also observed in the LSn. Using electron microscopic techniques, a few immunoreactive cell bodies were observed even in control animals. In addition, relatively numerous immunoreactive dendrites were observed in lamina II. The specificity of the reaction and the physiological implications of the results are discussed.
The effects of a single or repeated administrations of morphine on the tissue levels of cholecyst... more The effects of a single or repeated administrations of morphine on the tissue levels of cholecystokinin-like material (CCKLM) and pre pro cholecystokinin mRNA (CCK mRNA) were examined in various brain and spinal cord regions (cerebral cortex, cerebellum, hippocampus, septum, substantia nigra, lumbar enlargement) in adult rats using a specific radioimmunoassay and 'Northern blot' analysis, respectively. Although a clear parallelism existed between the regional distribution of CCKLM (septum greater than cerebral cortex greater than or equal to hippocampus much greater than lumbar enlargement, dorsal zone greater than substantia nigra greater than lumbar enlargement, ventral zone much much greater than cerebellum) and that of CCK mRNA, some mismatch was found notably in the septum where CCK mRNA levels were less than in other regions except the cerebellum. Neither CCKLM nor CCK mRNA levels were altered one hour after an acute administration of morphine (5 mg/kg i.p.). Similarly, morphine addiction after a four-day treatment with this drug was not associated with any change in the tissue levels of CCKLM and CCK mRNA. These data indicate that the previously reported modulatory action of opioids on central CCKergic systems could occur without affecting the preproCCK gene transcription and the tissue peptide concentrations.
: Biochemical mapping of five different peptide‐like materials—calcitonin gene‐related peptide (C... more : Biochemical mapping of five different peptide‐like materials—calcitonin gene‐related peptide (CGRP), substance P (SP), Met5‐enkephalin (ME), cholecystokinin (CCK), and dynorphin A (1–8) (DYN)—was conducted in the dorsal and ventral zones of the spinal cord at the cervical, thoracic, and lumbar levels in 3‐month‐old rats 10 days after unilateral dorsal rhizotomy at the cervical level (C4‐T2) or after neonatal administration of capsaicin (50 mg/kg s.c). In control rats, all peptide‐like materials were more abundant in the dorsal than in the ventral zone all along the spinal cord. However, in both zones, absolute concentrations of CGRP, SP, ME, and CCK were significantly higher at the lumbar than at the cervical level. Rhizotomy‐induced CGRP depletion (‐85%) within the ipsilateral dorsal zone of the cervical cord was more pronounced than that due to neonatal capsaicin (‐60%), a finding suggesting that this peptide is contained in both capsaicin‐sensitive (mostly unmyelinated) and ‐insensitive (myelinated) primary afferent fibers. In contrast, similar depletions of SP (‐50%) were observed after dorsal rhizotomy and neonatal capsaicin treatment, as expected from the presence of SP only in the capsaicin‐sensitive small‐diameter primary afferent fibers. Although the other three peptides remained unaffected all along the cord by either intervention, evidence for the existence of capsaicin‐insensitive CCKergic primary afferent fibers could be inferred from the increased accumulation of CCK (together with SP and CGRP) in dorsal root ganglia ipsilateral to dorsal root sections.
The possible modulation by κ 1 opioid receptor stimulation of the effects of μ receptor stimulati... more The possible modulation by κ 1 opioid receptor stimulation of the effects of μ receptor stimulation on the spinal release of met-enkephalin- (ME), substance P- (SP) μ calcitonin gene-related peptide- (CGRP) like materials (LM) was investigated in vivo in the rat. The stimulation of κ 1 receptors by 10 μM U 50488 H exerted no effect per se on the release processes. The stimulation of μ opioid receptors by 10 UM DAGO significantly reduced (-40%) the spinal outflow of MELM, enhanced (+44%) that of SPLM and did not affect CGRPLM outflow. In the presence of both DAGO and U 50488 H, the spinal release of MELM
Possible changes in the activity and opioid control of calcitonin gene-related peptide (CGRP)-con... more Possible changes in the activity and opioid control of calcitonin gene-related peptide (CGRP)-containing primary afferent fibers (PAF) were assessed in polyarthritic (PA) rats. Concentrations of CGRP-like material (CGRPLM) in the dorsal zone of the cervical and lumbar spinal cord and corresponding dorsal root ganglia (DRG) and preproCGRP mRNA levels in DRG were higher in PA rats than in age-paired control animals. The rate of the spontaneous spinal release of CGRPLM was ∼15 fold higher in PA rats than in controls. The blockade of μ opioid receptors by intrathecal perfusion with 10 μM naloxone produced a larger increase in the CGRPLM outflow in PA rats than in controls
The expression of the preproenkephalin A gene was investigated in adult rat dorsal root ganglia (... more The expression of the preproenkephalin A gene was investigated in adult rat dorsal root ganglia (DRG). A radioimmunoassayable Met-enkephalin (ME)-like material was detected in 0.1 M HCl extracts of rat DRG, representing approximately 60 pg of ME equivalents/mg of protein. Chromatographic analyses indicated that the major component of the ME-like material coeluted with authentic ME. In northern blot experiments on total RNA extracted from DRG, a cDNA probe corresponding to the entire coding region of rat preproenkephalin A mRNA yielded a single band of the expected size for this mRNA, i.e., 1.5 kb. Polymerase chain reaction (PCR) experiments were carried out with DRG, striatum, and liver cDNAs using two primers flanking the 1,371-1,771 base region of the preproenkephalin A gene. Thirty PCR cycles performed on both striatum and DRG cDNAs generated a single band of 400 bp, as expected, whereas only trace amounts of this product were detectable using liver cDNAs. Nucleotide sequencing of the PCR product obtained with DRG cDNAs revealed a 100% homology with the 1,371-1,771 sequence of the preproenkephalin A gene. In situ hybridization with a cRNA probe showed that about 3.5% of DRG cells expressed the preproenkephalin A transcript. However, most of these cells probably did not process proenkephalin to enkephalins, as thorough immunohistochemical investigations with anti-ME antibodies allowed the detection of only one in approximately 6,000 cells (in 30 sections of DRG) that exhibited ME-like immunoreactivity. Cells expressing preproenkephalin A mRNA were intermediate-sized neurons, suggesting that primary afferent ME-containing fibers belong to the A category and may participate in a local (spinal) inhibitory control of nociception.
RésuméLes interactions entre le système nerveux central et le système immunitaire ainsi que le rô... more RésuméLes interactions entre le système nerveux central et le système immunitaire ainsi que le rôle important des neurotransmetteurs et des cytokines dans cette communication bidirectionnelle sont aujourd’hui bien admis. Les deux systèmes synthétisent de surcroît certains médiateurs communs, telles les endomorphines dérivées de la proopiomélanocortine et de la proenképhaline A. Les résultats obtenus aussi bien chez l’animal in vivo que dans des expériencesin vitro suggèrent que les opioïdes (exogènes et endogènes) sont doués d’effets immunomodulateurs. L’action immunomodulatrice des morphiniques pourrait être indirecte, par le biais de récepteurs des opioïdes centraux, dont la sollicitation met en jeu des voies de signalisation qui ne sont que partiellement identifiées (axe hypothalamohypophysaire, système nerveux sympathique …), et directe, via les récepteurs des opioïdes des cellules immunocompétentes. La signification réelle des interactions entre opioïdes et système immunitaire n’est pas établie. Les travaux effectués chez l’homme n’apportent pas de réponse à cette question cruciale. De fait, force est de constater que peu d’études fiables (faible nombre de sujets, notamment…) ont été réalisées chez l’homme, et moins encore chez des patients douloureux traités de façon prolongée avec des morphiniques. Néanmoins, malgré leurs insuffisances, les données disponibles n’indiquent pas que les morphiniques au long cours aient des effets immunosuppresseurs majeurs, que ce soit chez des sujets exempts de douleur ou douloureux. Cette constatation peut être rapprochée du fait qu’aucune étude d’ordre épidémiologique n’a pu établir un lien entre toxicomanie aux opiacés et diminution du taux des cellules T CD4+ chez des patients séropositifs pour le VIH. Certains auteurs émettent d’ailleurs l’hypothèse générale que les opioïdes joueraient le rôle d’un frein homéostatique du système immunitaire qui permettrait en réalité à ce dernier d’être plus réactif lors d’une nouvelle agression. Ainsi, les données actuelles ne constituent pas un fort niveau de preuve en faveur d’effets délétères des morphiniques sur les défenses immunitaires des patients.SummaryThe existence of close interactions between central nervous and immune systems, as well as the preponderant action of neurotransmitters and cytokines in this cross-talk are well documented. In addition, both systems are endowed with several common mediators such as proopiomelanocortin-and proenkephalin A-derived opioid peptides. The immunomodulatory effects of opioids are supported by numerousin vivo andin vitro experimental data. This modulation could be elicited indirectly, via central opioid receptors stimulation and subsequent activation of different, only partially identified, pathways (hypothalamic-pituitary-adrenal axis, sympathetic innervation), or directly through the stimulation of opioid receptors located on immunocompetent cells.However, the physiological impact of this relationship is still unclear and available data from clinical trials do not supply an unequivocal answer. In fact, only few studies were carried out, most of those on healthy subjects and additional few on patients suffering from chronic painful conditions that were on long-term morphine treatment. Nevertheless, the data reported so far are not in favor of a major impact of prolonged opiates treatment on immune response either in subjects without pain or in patients suffering from painful conditions. It can be also pointed out that no epidemiological data exist to support some relation between opiates abuse and CD4+ T cells decreased levels in HIV positive patients. Several authors hypothesized that following the immune system activation, opioids might act as homeostatic regulators of immune system, thus increasing the reactivity and appropriate responses of the system to a novel aggression. Taking together, the available clinical data do not clearly evidence the existence of some deleterious effect of opiates on patients immune defense.
Calcitonin gene-related peptide (CGRP) in the dorsal horn of the rat spinal cord was assumed unti... more Calcitonin gene-related peptide (CGRP) in the dorsal horn of the rat spinal cord was assumed until now to be principally of primary afferent origin. It is shown here, on the basis of both light and electron microscopic immunocytochemical evidence, that some cell bodies of the dorsal horn and lateral spinal nucleus (LSn) of the rat cervical spinal cord contain a CGRP-like immunoreactivity. At the light microscopic level, immunoreactive cell bodies were observed in animals pretreated with colchicine injected intraventricularly, CGRP-like cell bodies were morphologically heterogeneous and distributed in the three superficial layers of the dorsal horn. They were very rare in lamina I and more numerous in laminae II and III. A group of immunoreactive cell bodies was also observed in the LSn. Using electron microscopic techniques, a few immunoreactive cell bodies were observed even in control animals. In addition, relatively numerous immunoreactive dendrites were observed in lamina II. The specificity of the reaction and the physiological implications of the results are discussed.
The effects of a single or repeated administrations of morphine on the tissue levels of cholecyst... more The effects of a single or repeated administrations of morphine on the tissue levels of cholecystokinin-like material (CCKLM) and pre pro cholecystokinin mRNA (CCK mRNA) were examined in various brain and spinal cord regions (cerebral cortex, cerebellum, hippocampus, septum, substantia nigra, lumbar enlargement) in adult rats using a specific radioimmunoassay and 'Northern blot' analysis, respectively. Although a clear parallelism existed between the regional distribution of CCKLM (septum greater than cerebral cortex greater than or equal to hippocampus much greater than lumbar enlargement, dorsal zone greater than substantia nigra greater than lumbar enlargement, ventral zone much much greater than cerebellum) and that of CCK mRNA, some mismatch was found notably in the septum where CCK mRNA levels were less than in other regions except the cerebellum. Neither CCKLM nor CCK mRNA levels were altered one hour after an acute administration of morphine (5 mg/kg i.p.). Similarly, morphine addiction after a four-day treatment with this drug was not associated with any change in the tissue levels of CCKLM and CCK mRNA. These data indicate that the previously reported modulatory action of opioids on central CCKergic systems could occur without affecting the preproCCK gene transcription and the tissue peptide concentrations.
: Biochemical mapping of five different peptide‐like materials—calcitonin gene‐related peptide (C... more : Biochemical mapping of five different peptide‐like materials—calcitonin gene‐related peptide (CGRP), substance P (SP), Met5‐enkephalin (ME), cholecystokinin (CCK), and dynorphin A (1–8) (DYN)—was conducted in the dorsal and ventral zones of the spinal cord at the cervical, thoracic, and lumbar levels in 3‐month‐old rats 10 days after unilateral dorsal rhizotomy at the cervical level (C4‐T2) or after neonatal administration of capsaicin (50 mg/kg s.c). In control rats, all peptide‐like materials were more abundant in the dorsal than in the ventral zone all along the spinal cord. However, in both zones, absolute concentrations of CGRP, SP, ME, and CCK were significantly higher at the lumbar than at the cervical level. Rhizotomy‐induced CGRP depletion (‐85%) within the ipsilateral dorsal zone of the cervical cord was more pronounced than that due to neonatal capsaicin (‐60%), a finding suggesting that this peptide is contained in both capsaicin‐sensitive (mostly unmyelinated) and ‐insensitive (myelinated) primary afferent fibers. In contrast, similar depletions of SP (‐50%) were observed after dorsal rhizotomy and neonatal capsaicin treatment, as expected from the presence of SP only in the capsaicin‐sensitive small‐diameter primary afferent fibers. Although the other three peptides remained unaffected all along the cord by either intervention, evidence for the existence of capsaicin‐insensitive CCKergic primary afferent fibers could be inferred from the increased accumulation of CCK (together with SP and CGRP) in dorsal root ganglia ipsilateral to dorsal root sections.
The possible modulation by κ 1 opioid receptor stimulation of the effects of μ receptor stimulati... more The possible modulation by κ 1 opioid receptor stimulation of the effects of μ receptor stimulation on the spinal release of met-enkephalin- (ME), substance P- (SP) μ calcitonin gene-related peptide- (CGRP) like materials (LM) was investigated in vivo in the rat. The stimulation of κ 1 receptors by 10 μM U 50488 H exerted no effect per se on the release processes. The stimulation of μ opioid receptors by 10 UM DAGO significantly reduced (-40%) the spinal outflow of MELM, enhanced (+44%) that of SPLM and did not affect CGRPLM outflow. In the presence of both DAGO and U 50488 H, the spinal release of MELM
Possible changes in the activity and opioid control of calcitonin gene-related peptide (CGRP)-con... more Possible changes in the activity and opioid control of calcitonin gene-related peptide (CGRP)-containing primary afferent fibers (PAF) were assessed in polyarthritic (PA) rats. Concentrations of CGRP-like material (CGRPLM) in the dorsal zone of the cervical and lumbar spinal cord and corresponding dorsal root ganglia (DRG) and preproCGRP mRNA levels in DRG were higher in PA rats than in age-paired control animals. The rate of the spontaneous spinal release of CGRPLM was ∼15 fold higher in PA rats than in controls. The blockade of μ opioid receptors by intrathecal perfusion with 10 μM naloxone produced a larger increase in the CGRPLM outflow in PA rats than in controls
The expression of the preproenkephalin A gene was investigated in adult rat dorsal root ganglia (... more The expression of the preproenkephalin A gene was investigated in adult rat dorsal root ganglia (DRG). A radioimmunoassayable Met-enkephalin (ME)-like material was detected in 0.1 M HCl extracts of rat DRG, representing approximately 60 pg of ME equivalents/mg of protein. Chromatographic analyses indicated that the major component of the ME-like material coeluted with authentic ME. In northern blot experiments on total RNA extracted from DRG, a cDNA probe corresponding to the entire coding region of rat preproenkephalin A mRNA yielded a single band of the expected size for this mRNA, i.e., 1.5 kb. Polymerase chain reaction (PCR) experiments were carried out with DRG, striatum, and liver cDNAs using two primers flanking the 1,371-1,771 base region of the preproenkephalin A gene. Thirty PCR cycles performed on both striatum and DRG cDNAs generated a single band of 400 bp, as expected, whereas only trace amounts of this product were detectable using liver cDNAs. Nucleotide sequencing of the PCR product obtained with DRG cDNAs revealed a 100% homology with the 1,371-1,771 sequence of the preproenkephalin A gene. In situ hybridization with a cRNA probe showed that about 3.5% of DRG cells expressed the preproenkephalin A transcript. However, most of these cells probably did not process proenkephalin to enkephalins, as thorough immunohistochemical investigations with anti-ME antibodies allowed the detection of only one in approximately 6,000 cells (in 30 sections of DRG) that exhibited ME-like immunoreactivity. Cells expressing preproenkephalin A mRNA were intermediate-sized neurons, suggesting that primary afferent ME-containing fibers belong to the A category and may participate in a local (spinal) inhibitory control of nociception.
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