RESUMEN
BACKGROUND: Hyperalgesia that develops following nerve ligation corresponds temporally and in magnitude with the number of thalamic mast cells located contralateral to the ligature. We tested the possibility that mast cells modulate nociception centrally, similar to their role in the periphery. METHODS: We examined the central effect of two hyperalgesic compounds that induce mast cell degranulation and of stabilized mast cells using cromolyn. RESULTS: Thermal hyperalgesia (tail flick) induced by nerve growth factor (NGF, a neurotrophic compound) and mechanical hyperalgesia (von Frey) induced by dynorphin A (1-17) (opioid compound) each correlated with the per cent of thalamic mast cells that were degranulated. Degranulation of these mast cells by the central injection of compound 48/80, devoid of neurotrophic or opioid activity, was sufficient to recapitulate thermal hyperalgesia. Stabilization of mast cells by central injections of cromolyn produced no analgesic effect on baseline tail flick or von Frey fibre sensitivity, but inhibited thermal hyperalgesia produced by compound 48/80 and tactile hyperalgesia induced by dynorphin and by Freund's complete adjuvant. Finally, chemical nociception produced by the direct activation of nociceptors by formalin (phase I) was not inhibited by centrally injected cromolyn whereas chemical nociception dependent on central sensitization (formalin-phase II and acetic acid-induced abdominal stretches) was. CONCLUSIONS: These convergent lines of evidence suggest that degranulation of centrally located mast cells sensitizes central nociceptive pathways leading to hyperalgesia and tonic chemical sensitivity. SIGNIFICANCE: Hyperalgesia induced by spinal nerve ligation corresponds temporally and in magnitude with degranulation of thalamic mast cells. Here, we provide evidence that hyperalgesia induced by NGF, formalin and dynorphin also may depend on mast cell degranulation in the CNS whereas cromolyn, a mast cell stabilizer, blocks these effects in mice.
Asunto(s)
Hiperalgesia/patología , Hiperalgesia/fisiopatología , Mastocitos/fisiología , Nocicepción/fisiología , Animales , Recuento de Células , Cromolin Sódico , Modelos Animales de Enfermedad , Dinorfinas , Hiperalgesia/etiología , Masculino , Ratones , Factor de Crecimiento Nervioso , Neurotransmisores , Nociceptores/fisiologíaRESUMEN
The opioid peptide dynorphin has been demonstrated to be both nociceptive and antinociceptive. This article will review the potential mechanisms through which dynorphin contributes to spinally mediated nociception. Specifically, we will examine the interaction of dynorphin with multiple sites on the NMDA receptor complex. Dynorphin-induced opioid activity is generally inhibitory, with a tendency to impede nociceptive signals and serve in a neuroprotective capacity. In contrast, dynorphin's interaction with multiple sites on the NMDA receptor complex produces excitatory responses resulting in nociceptive and even toxic effects. Thus, it is hypothesized that dynorphin has both physiological and pathological roles in acute and chronic pain states.
Asunto(s)
Analgésicos Opioides/farmacología , Dinorfinas/farmacología , Analgésicos Opioides/metabolismo , Animales , Dinorfinas/metabolismo , Humanos , Receptores de N-Metil-D-Aspartato/efectos de los fármacos , Receptores Opioides/efectos de los fármacosRESUMEN
Nitric oxide (NO) in the spinal cord plays a role in sensory and autonomic activity. Pain induced by acetic acid in the abdominal stretch (writhing) assay and hyperalgesia associated with chronic pain are highly sensitive to NO synthase (NOS) inhibitors. Because substance P (SP) is released and up-regulated in some models of chronic pain, we hypothesized that an accumulation of SP metabolites may influence NOS expression and activity. To test this hypothesis, we examined the effect of intrathecally (i.t.) injected substance P (1-7) [SP(1-7)], the major metabolite of SP in the rat, on neuronal NOS (nNOS) mRNA in the thoracic and lumbar spinal cord, dorsal root ganglia (DRG) and on the corresponding constitutive NOS (cNOS) enzyme activity. Detected using quantitative RT-PCR, nNOS mRNA content in the thoracic spinal cord was decreased 6 h after injection of 5 micromol of SP(1-7) and returned to control 2 days later. In thoracic DRG, nNOS mRNA was reduced 48 h after SP(1-7). The cNOS enzymatic activity in thoracic spinal tissue was gradually decreased to a minimum at 72 h. Down-regulation of NOS by SP(1-7) in the thoracic area appears to be highly associated with capsaicin-sensitive primary afferent neurons. No similar changes in either parameter were measured in the lumbar area after SP(1-7). These data suggest that N-terminal SP fragments, which are known to cause long-term antinociception in the writhing assay, may do so by their ability to down-regulate NO synthesis along nociceptive pathways.
Asunto(s)
Ganglios Espinales/enzimología , Óxido Nítrico Sintasa/genética , Óxido Nítrico/metabolismo , Dolor/enzimología , Fragmentos de Péptidos/farmacología , ARN Mensajero/metabolismo , Médula Espinal/enzimología , Sustancia P/farmacología , Animales , Arginina/farmacología , Capsaicina/farmacología , Ganglios Espinales/citología , Ganglios Espinales/efectos de los fármacos , Vértebras Lumbares , Masculino , Degeneración Nerviosa/inducido químicamente , Degeneración Nerviosa/enzimología , Degeneración Nerviosa/fisiopatología , Fibras Nerviosas/efectos de los fármacos , Fibras Nerviosas/enzimología , Fibras Nerviosas/patología , Neuronas Aferentes/citología , Neuronas Aferentes/efectos de los fármacos , Neuronas Aferentes/enzimología , Nociceptores/citología , Nociceptores/efectos de los fármacos , Nociceptores/enzimología , Dolor/genética , Dolor/fisiopatología , Fragmentos de Péptidos/metabolismo , Ratas , Ratas Sprague-Dawley , Médula Espinal/citología , Médula Espinal/efectos de los fármacos , Sustancia P/metabolismo , Vértebras TorácicasRESUMEN
Although characterized by a variety of symptoms, chronic widespread pain is the primary complaint bringing most patients with fibromyalgia syndrome (FMS) into the clinic. The etiology of this painful condition is unknown, and any possible relationship between pain and the many other symptoms of FMS is unclear. This article focuses on the unique characteristics of nociception in patients with FMS. The intent is to present criteria that should be considered in the search for biological events that contribute to FMS pain. Based on this approach, examples are proposed of factors that fulfill some criteria and may, therefore, deserve further study for their possible role in pain associated with FMS.
Asunto(s)
Fibromialgia/etiología , Neuralgia/complicaciones , Neuralgia/fisiopatología , Nociceptores/fisiopatología , Fibromialgia/fisiopatología , Humanos , Factores de RiesgoRESUMEN
Vesicular Zn2+, released in the brain and from small dorsal root ganglion neurons, interacts with opioid as well as N-methyl-D-aspartate (NMDA) receptors. We investigated the effect of Zn2+ on morphine antinociception in mice (tail flick assay), as well as acute tolerance and dependence, phenomena associated with NMDA activity. Administered intrathecally (i.t.), Zn2+ inhibited morphine antinociception in a dose-related fashion. Zn2+ also inhibited acute tolerance to morphine antinociception (5 h after 100 mg/kg of morphine). Injection i.t. of di-sodium calcium ethylenediamine tetra acetic acid (Na+Ca2+ EDTA), a chelator of divalent cations, had no effect on analgesia, acute tolerance or acute dependence. However, withdrawal jumps produced by naloxone (1 mg/kg s.c.) in morphine-pellet implanted mice (3 days) were potentiated by injections twice daily of 10 nmol of Na+Ca2+ EDTA, suggesting that endogenous Zn2+ tends to inhibit long-term development of withdrawal. These data suggest that the availability of Zn2+ is an important factor in opioid activity.
Asunto(s)
Analgésicos Opioides/farmacología , Cloruros/administración & dosificación , Tolerancia a Medicamentos/fisiología , Morfina/farmacología , Dimensión del Dolor/efectos de los fármacos , Úlcera Cutánea/tratamiento farmacológico , Compuestos de Zinc/administración & dosificación , Animales , Quelantes/farmacología , Cloruros/farmacología , Interacciones Farmacológicas , Ácido Edético/farmacología , Inyecciones Espinales , Masculino , Ratones , Compuestos de Zinc/farmacologíaRESUMEN
A single injection of nitric oxide (NO) synthase (NOS) inhibitors prevents the development of persistent hyperalgesia induced by various manipulations, suggesting that NO precipitates long-term changes in nociception. We examined the possibility that inhibition of NOS may also be sufficient to produce long-term decreases in nociceptive assays, such as writhing, that are known to be sensitive to the short-term effects of NOS inhibitors. We characterized short- and long-term effects of NOS inhibitors, N(omega)-nitro-L-arginine (L-NAME) or 7-nitro indazole (7-NI) injected intrathecally (i.t.) in mice on acetic acid-induced writhing. Doses of L-NAME that had no effect on hot plate or tail flick latencies inhibited writhing (0. 01-30 nmol) as well as spinal nNOS activity (5 and 100 nmol) when injected i.t. 60-90 min before testing. Anti-nociception was not mimicked by D-NAME but was prevented by co-administration with the NO precursor, L-arginine. Injection i.t. of 7-NI (30 min), a selective inhibitor of neuronal NOS (nNOS), inhibited NOS activity in the spinal cord and produced anti-nociception, confirming that writhing is sensitive to inhibition of nNOS. Although the acute action of both NOS inhibitors dissipated completely by 3-6 h, a delayed and prolonged inhibition of writhing was again observed 24 h after L-NAME (5-100 nmol), a time when spinal NOS activity was no longer inhibited by L-NAME (5 and 100 nmol) or 7-NI (25 nmol). This novel effect appears to be initiated by the transient inhibition of nNOS as delayed anti-nociception was mimicked by 7-NI at doses (10-100 nmol) that no longer inhibited spinal nNOS (25 nmol) at 24 h. Co-administration with L-arginine prevented the delayed (24 h) anti-nociceptive effects of L-NAME (30 nmol). L-Arginine (30 and 100 nmol) was without effect on nociception when administered alone 60 min or 24 h prior to testing. Together these data indicate that brief changes in the activity of nNOS induce both long- as well as short-term changes in nociception.
Asunto(s)
Ácido Acético , Óxido Nítrico/biosíntesis , Dimensión del Dolor/efectos de los fármacos , Animales , Arginina/farmacología , Conducta Animal/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Inhibidores Enzimáticos/administración & dosificación , Inhibidores Enzimáticos/farmacología , Calor , Indazoles/administración & dosificación , Indazoles/farmacología , Inyecciones Espinales , Masculino , Ratones , NG-Nitroarginina Metil Éster/administración & dosificación , NG-Nitroarginina Metil Éster/farmacología , Óxido Nítrico Sintasa/antagonistas & inhibidores , Óxido Nítrico Sintasa/metabolismo , Óxido Nítrico Sintasa de Tipo II , Óxido Nítrico Sintasa de Tipo III , Tiempo de Reacción/efectos de los fármacos , Médula Espinal/efectos de los fármacos , Médula Espinal/enzimologíaRESUMEN
Kainic acid produces a persistent hyperalgesia when injected intraperitoneally (i.p.) in the rat or mouse. At higher doses than those needed to influence nociception, kainic acid induces seizures and translocation of histologically reactive zinc in the hippocampus. We tested the hypothesis that zinc, localized in a population of small diameter primary afferent neurons, plays a role in kainic acid-induced hyperalgesia similar to that in the hippocampus where zinc translocation accompanies kainic acid-induced seizures. The importance of zinc in the extracellular area was assessed by the influence of compounds that chelate divalent cations (disodium calcium ethylene diaminetetraacetate (CaEDTA)) or zinc (dipicolinic acid (DPA)) on kainic acid-induced hyperalgesia. When measured using the tail flick assay, thermal hyperalgesia was blocked by pretreatment intrathecally (i.t.) with either 10 nmol of NaCaEDTA or 1 nmol of DPA, drugs whose distribution is limited to the extracellular area. Injection of 10 ng zinc chloride i.t. had no long-term effect on nociception or on kainic acid-induced hyperalgesia. Whether zinc is translocated in response to a hyperalgesic dose of kainic acid was determined using the zinc-selective dye, N-(6-methoxy-8-quinolyl)-para-toluenensulfonamide (TSQ), which produces a delicate stain in the neuropil of the mouse spinal cord as well as a dense stain in the hippocampus. Injection of a hyperalgesic dose of kainic acid failed to alter TSQ fluorescence in either the spinal cord or hippocampus, in contrast to the distinct bleaching of TSQ in the hippocampus 24 h after a convulsant dose of kainic acid. Together these data suggest that, while not translocated, zinc in the extracellular area is necessary but not sufficient for the development of kainic acid-induced hyperalgesia.
Asunto(s)
Sistema Nervioso Central/fisiología , Agonistas de Aminoácidos Excitadores , Hiperalgesia/inducido químicamente , Hiperalgesia/fisiopatología , Ácido Kaínico , Zinc/fisiología , Aminoquinolinas , Animales , Conducta Animal/efectos de los fármacos , Cationes Bivalentes , Sistema Nervioso Central/metabolismo , Quelantes/administración & dosificación , Quelantes/farmacología , Enfermedad Crónica , Ácido Edético/administración & dosificación , Ácido Edético/farmacología , Espacio Extracelular/metabolismo , Espacio Extracelular/fisiología , Colorantes Fluorescentes , Hiperalgesia/psicología , Inyecciones Espinales , Masculino , Ratones , Tiempo de Reacción/efectos de los fármacos , Compuestos de Tosilo , Zinc/metabolismo , Zinc/farmacologíaRESUMEN
Nociceptive primary afferent C-fibers express a subset of glutamate receptors that are sensitive to kainic acid. Thus, we tested the possibility that activation of these receptors alters nociception. Intraperitoneal (i.p.) injection of kainic acid induced a persistent thermal hyperalgesia, when tested using the hot plate (mice) and tail flick (mice and rats) assays, and mechanical hyperalgesia when tested using von Frey monofilaments (rats), but had no effect on acetic acid-induced chemical nociception (mice). When administered i. p., 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX), an (R, S)-alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid HBr/kainate (AMPA/KA) antagonist, completely blocked hyperalgesia. When injected intrathecally (i.t.), kainic acid itself failed to induce hyperalgesia and AMPA/KA antagonists given i.t. also failed to attenuate the hyperalgesic effect of kainic acid administered i.p. , indicating that the spinal cord is not the primary site of action. Kainic acid injected subcutaneously in the back of mice decreased response latencies in the hot plate and tail flick assays, indicating that hyperalgesia is achieved by a variety of parenteral routes of injection. Histological evaluation of rat spinal cord and dorsal root ganglia revealed no neurodegenerative changes 24 h after kainic acid. Together these data suggest that a persistent hyperalgesia results from the transient activation of AMPA/KA receptors that are located outside the spinal cord, perhaps on the distal projections of primary afferent fibers.
Asunto(s)
Hiperalgesia/fisiopatología , Ácido Kaínico/farmacología , 6-Ciano 7-nitroquinoxalina 2,3-diona/farmacología , Animales , Agonistas de Aminoácidos Excitadores/administración & dosificación , Agonistas de Aminoácidos Excitadores/farmacología , Antagonistas de Aminoácidos Excitadores/farmacología , Miembro Posterior , Calor , Hiperalgesia/inducido químicamente , Inyecciones Intraperitoneales , Ácido Kaínico/administración & dosificación , Masculino , Ratones , Ratones Endogámicos , Estimulación Física , Piperazinas/farmacología , Ratas , Ratas Sprague-Dawley , TactoRESUMEN
OBJECTIVE: To determine whether there is a difference in the concentration of nerve growth factor (NGF) in the cerebrospinal fluid (CSF) from patients diagnosed with primary fibromyalgia syndrome (FM), fibromyalgia associated with other secondary conditions (SFM), patients with other painful conditions but lacking fibromyalgia (OTHER), and healthy controls. METHODS: The clinical measures of pain threshold included the tender point index, a measure of pain threshold intensity measured by digital pressure, and the average pain threshold measured by dolorimetry. Concentrations of NGF in the CSF were measured using a 2 site enzyme immunoassay. RESULTS: The mean (+/- SEM) concentration of NGF measured in patients with FM was significantly increased (41.8 +/- 12.7 pg/ml) compared to controls (9.1 +/- 4.1 pg/ml), but with large variability. Concentrations of NGF is SFM (8.9 +/- 4.4 pg/ml) and OTHER (16.2 +/- 8.4 pg/ml) were not elevated compared to controls. CONCLUSION: The findings of increased concentrations of NGF in patients with FM suggest a central mechanism, involving abnormalities in neuropeptides such as NGF, may be a factor in the pathogenesis of FM.
Asunto(s)
Fibromialgia/líquido cefalorraquídeo , Factor de Crecimiento Nervioso/líquido cefalorraquídeo , Adolescente , Adulto , Femenino , Fibromialgia/fisiopatología , Humanos , Inmunoensayo , Masculino , Persona de Mediana Edad , Umbral del DolorRESUMEN
Zinc appears to play a role in synaptic transmission in the hippocampus. We tested the hypothesis that zinc is similarly involved in sensory transmission by determining whether vesicular zinc and metallothionein-III (MT-III), a zinc-binding protein, are localized in rat primary afferent neurons. MT-III mRNA, measured using RT-PCR, and MT-III immunoreactivity, were both present in the spinal cord as well as the thoracic and lumbar dorsal root ganglia (DRG). At a time (24 hr) that allows retrograde transport of zinc selenite to cell bodies, only small-diameter neurons and neurons scattered throughout lamina V of the spinal cord were stained by sodium selenite injected intrathecally. This stain disappeared if a ligature was placed on the dorsal root to block axonal transport, demonstrating that these cells are, in fact, zinc-containing primary afferent neurons. When assessed 1 hr after sodium selenite, stain was distributed throughout the neuropil of the spinal cord, especially in lamina III and the area surrounding the central canal. Even in rhizotomized animals, large- and small-diameter DRG neuronal cell bodies were also stained with either selenite (1 hr) or 6-methoxy 8-para-toluene sulfonamide quinoline (TSQ). Paradoxically, this unique pool of zinc was eliminated in large-diameter DRG neurons after neonatal capsaicin treatment, which had no effect on selenite stain or MT-III mRNA content in small-diameter DRG neurons. In summary, we demonstrate that there is a population of capsaicin-insensitive small-diameter primary afferent neurons that are zinc-containing. In addition, there is a unique pool of capsaicin-sensitive zinc that is associated with large-diameter cell bodies.
Asunto(s)
Ganglios Espinales/metabolismo , Proteínas del Tejido Nervioso/metabolismo , Compuestos de Selenio/metabolismo , Sensación/fisiología , Médula Espinal/metabolismo , Transmisión Sináptica/fisiología , Compuestos de Zinc/metabolismo , Zinc/fisiología , Animales , Esquema de Medicación , Inmunohistoquímica , Masculino , Metalotioneína 3 , Proteínas del Tejido Nervioso/genética , ARN Mensajero/metabolismo , Ratas , Ratas Sprague-Dawley , Rizotomía , Selenito de Sodio/administración & dosificación , Selenito de Sodio/farmacología , Distribución TisularRESUMEN
Capsaicin depolarizes primary afferent C-fibers releasing substance P (SP) whose N-terminal metabolites appear to play a role in the development of antinociception. Because some effects of SP(1-7) are similar to those of zinc, we tested the hypothesis that zinc in the extracellular area plays a role in capsaicin-induced antinociception, as measured using the abdominal stretch (writhing) assay. Decreases in zinc were achieved by intrathecal (i.t.) injection of membrane-impermeable compounds: ethylenediaminetetraacetic acid disodium-calcium salt (Ca++ EDTA), a calcium-saturated chelator of divalent cations, or dipicolinic acid, a zinc chelator. Ten nanomoles of Ca++ EDTA had no effect on writhing at either 90 min or 24 h after injection, yet pretreatment with Ca++ EDTA prevented the development of antinociception 24 h after i.t. injection of either 2. 8 nmol of capsaicin or 10 nmol of SP(1-7). One nanomole of dipicolinic acid injected i.t. also blocked capsaicin- and SP(1-7)-induced antinociception. When injected 24 h after SP(1-7), Ca++ EDTA failed to reverse antinociception. Acute antinociception produced 30 min after injection of SP(1-7) was also blocked when Ca++ EDTA was injected 24 h, but not 60 min, before SP(1-7). Thus, the optimal time of Ca++ EDTA-induced hyperalgesia (90 min), described previously, did not correspond to that of its inhibitory effect on antinociception (24 h). In contrast, we found that the previously described antinociception after an i.t. injection of zinc (90 min) is greatly attenuated by 24 h. Thus, zinc appears to be necessary, but may not be sufficient, for the long-term antinociceptive effect of capsaicin, acting downstream from the action of substance P N-terminal metabolites.
Asunto(s)
Capsaicina/antagonistas & inhibidores , Quelantes/farmacología , Ácido Edético/farmacología , Nociceptores/efectos de los fármacos , Ácidos Picolínicos/farmacología , Médula Espinal/efectos de los fármacos , Zinc/metabolismo , Ácido Acético/farmacología , Animales , Capsaicina/farmacología , Interacciones Farmacológicas , Espacio Extracelular/metabolismo , Masculino , Ratones , Ratones Endogámicos , Dimensión del Dolor/efectos de los fármacos , Fragmentos de Péptidos/farmacología , Médula Espinal/metabolismo , Sustancia P/farmacología , Zinc/fisiologíaRESUMEN
To monitor the possible effect of morphine on sigma sites, binding characteristics of [3H](+)-pentazocine and [3H]1,3-di-(2-tolyl)guanidine (DTG) to brain and spinal cord membranes of morphine-treated and control mice were compared. For morphine treatment, a single injection (100 mg/kg, s.c.) of morphine was followed 4 h later by pellet implantation (75 mg morphine free base). Animals were sacrificed 24, 72 h or 7 days later. The equilibrium dissociation value (Kd) and the density (Bmax) of [3H](+)-pentazocine binding remained unaffected by morphine treatment. Also, no change was found in Kd and Bmax values of [3H]DTG labeled sigma2 subtypes after any morphine treatment schedule when measured in the presence of 100 nM (+)-pentazocine. However, the Bmax of [3H]DTG binding in the spinal cord in the absence of 100 nM (+)-pentazocine, was significantly elevated 72 h after implantation of the morphine pellet and recovered by 7 days, a time when the antinociceptive effect produced by the morphine pellet had dissipated. These data suggest that one population of sigma sites, that has a high affinity for [3H]DTG, but is not equivalent with the [3H](+)-pentozocine labeled sigma1 subtype or the [3H]DTG labeled sigma2 subtype, is upregulated by morphine and, therefore, may play a role in the development of tolerance to or dependence on the effects of morphine.
Asunto(s)
Morfina/farmacología , Receptores sigma/metabolismo , Médula Espinal/efectos de los fármacos , Médula Espinal/metabolismo , Análisis de Varianza , Animales , Corteza Cerebral/efectos de los fármacos , Corteza Cerebral/metabolismo , Tolerancia a Medicamentos , Guanidinas/metabolismo , Masculino , Ratones , Dependencia de Morfina , Narcóticos/farmacología , Pentazocina/metabolismoRESUMEN
The role of metabotropic glutamate receptors in the processing of somatosensory information was studied in dorsal horn neurons of the rat spinal cord. Activation of metabotropic glutamate receptors by local iontophoresis of (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid resulted in an increased response of dorsal horn neurons to ionotropic glutamate receptor agonists (N-methyl-D-aspartate and kainic acid) applied by iontophoresis. Greater amounts of 1S,3R-1-amino-cyclopentane-1,3-dicarboxylic acid, ejected at high iontophoresis currents, directly excited dorsal horn neurons. Application of (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid also led to a significant increase in responses to innocuous (brush, pressure) but not in responses to noxious (pinch, squeeze) mechanical stimulation. The excitatory effects of (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid were selectively blocked by (S)-4-carboxy-3-hydroxyphenyl-glycine, an antinociceptive phenylglycine derivative which is a selective group 1 metabotropic glutamate receptor antagonist, confirming the involvement of these receptors. In wide dynamic range neurons, wind-up, the progressive potentiation of C-fibre-evoked responses during a train of stimuli, was increased by iontophoretic application of (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid or decreased by iontophoresis of (S)-4-carboxy-3-hydroxyphenyl-glycine without significant change in the C-fibre input. The results suggest an interaction between metabotropic and ionotropic glutamate receptors in spinal dorsal horn neurons. Metabotropic glutamate receptors proved to be involved in the frequency-dependent potentiation of C-fibre responses possibly via modulation of ionotropic glutamate receptors. The long-lasting effects of (1S,3R)-1-amino-cyclopentane-1,3-dicarboxylic acid on wind-up and on responses to peripheral mechanical stimuli strongly support the view that metabotropic glutamate receptors in these neurons may play a significant role in spinal synaptic plasticity, and therefore, may contribute to the central sensitization during mechanical hyperalgesia.
Asunto(s)
Neuronas Aferentes/fisiología , Receptores de Glutamato Metabotrópico/fisiología , Médula Espinal/fisiología , Transmisión Sináptica/fisiología , Animales , Cicloleucina/análogos & derivados , Cicloleucina/farmacología , Agonistas de Aminoácidos Excitadores/farmacología , Espacio Extracelular/efectos de los fármacos , Espacio Extracelular/fisiología , Iontoforesis , Ácido Kaínico/farmacología , Masculino , N-Metilaspartato/farmacología , Fibras Nerviosas/efectos de los fármacos , Fibras Nerviosas/fisiología , Estimulación Física , Ratas , Ratas Sprague-Dawley , Receptores de Glutamato Metabotrópico/agonistas , Médula Espinal/citologíaRESUMEN
Substance P (SP) N-terminal fragments are known to alter nociception when injected intrathecally or when released in response to capsaicin. However, it is not known whether a sufficient concentration of SP N-terminal metabolites accumulate during noxious stimulation to modulate nociception. To test this, we examined the effect of the SP(1-7) antagonist, D-SP(1-7), injected intrathecally in mice, on two nociceptive assays that are differentially affected by exogenous SP(1-7): acetic acid-induced writhing that is inhibited and formalin-induced behaviors that are enhanced by SP(1-7). One nmol of D-SP(1-7) is sufficient to block the acute (30 min) antinociceptive effects of SP(1-7) on writhing. When injected alone at much higher doses (10-100 nmol), D-SP(1-7) inhibited writhing. In the formalin assay, SP(1-7) had no acute effect (30 min) on responses during Phase 1 at any dose tested, but D-SP(1-7) increased responses 5 min after injection of low (2-1000 pmol), but not high doses (10 and 100 nmol). Twenty-four hours after injection of SP(1-7), writhing was inhibited and formalin responses were increased. D-SP(1-7) prevented these effects of SP(1-7) but had no effect when injected alone, indicating that there is no tonic SP N-terminal activity in mice not exposed to noxious stimuli. Thus, acetic acid and formalin each induce endogenous SP N-terminal activity, respectively, producing a pro-nociceptive effect that is relatively insensitive to D-SP(1-7) and antinociception that is very sensitive to inhibition by D-SP(1-7).
Asunto(s)
Dolor/fisiopatología , Fragmentos de Péptidos/antagonistas & inhibidores , Fragmentos de Péptidos/farmacología , Sustancia P/química , Sustancia P/farmacología , Análisis de Varianza , Animales , Relación Dosis-Respuesta a Droga , Hiperalgesia/tratamiento farmacológico , Inyecciones Espinales , Masculino , Ratones , Dimensión del Dolor , Estimulación QuímicaRESUMEN
Although loss of heterozygosity (LOH) for loci on chromosome 3p is a common event in cervical carcinoma (CC), the frequency and affected regions of 3p are inconsistent among studies. Here we report a comprehensive analysis of LOH on 3p in 66 primary tumors and 16 CC-derived cell lines using a high density of marker loci. Clonal LOH was found in over 70% of primary tumors, and the patterns of loss indicated four to five target regions, with 3p14 being the most frequent. The majority of tumors had complex patterns of allelic imbalance, with regions of subclonal and clonal losses often present in individual tumors. We exploited marker homozygosity in CC-derived cell lines as an indirect measure of LOH and identified four homozygous deletions (HDs) during this analysis at loci located within the 3p14.2 region to which the FHIT gene has been mapped recently. This led to a careful reevaluation of the LOH patterns in primary CCs, which showed apparent retention of heterozygosity for loci in this region indicative of the presence of several additional HDs. To our knowledge, this is the first report of HDs encompassing the FHIT gene region in primary tumor samples and underscores the usefulness of high resolution genetic analysis of tumor genomes in determining the chromosomal aberrations underlying the malignant progression of CC.
Asunto(s)
Carcinoma/genética , Cromosomas Humanos Par 3 , Neoplasias del Cuello Uterino/genética , Alelos , Mapeo Cromosómico , Células Clonales , ADN de Neoplasias/genética , Femenino , Marcadores Genéticos , Heterocigoto , Humanos , Repeticiones de Microsatélite , Eliminación de SecuenciaRESUMEN
Carcinomas of the uterine cervix are thought to arise from preinvasive dysplastic lesions, termed cervical intraepithelial neoplasias (CIN), grades I-III. Patients may present clinically with two or more distinct lesions of differing histological severity; however, the genesis of these multifocal lesions is unknown. Despite infection with high-risk human papilloma virus subtypes, which is a major etiological factor in disease pathogenesis, only a small and unpredictable number of dysplastic lesions progress to invasive cancer. Several lines of evidence suggest that additional somatic events, such as tumor suppressor gene inactivation, are required for malignant transformation. In support of this, loss of heterozygosity (LOH) analyses of invasive cervical carcinomas have identified several chromosomal arms likely to harbor tumor suppressor genes, of which regions on 3p, 4p, 4q, and 11q have been validated extensively. To evaluate the potential role of tumor suppressor gene inactivation in dysplastic progression, loci distributed on these four chromosomal regions were assessed for LOH in 42 CIN lesions of varying histological grade obtained from 17 patients. Analysis of at least 16 microsatellite loci in each lesion revealed allelic losses involving one or more of these chromosomal regions in 0% of CIN I lesions; 25% of CIN II lesions; and 88% of CIN III lesions, with 41% of CIN III lesions exhibiting LOH for three or more chromosomal regions. In addition, where LOH was scored for the same locus at a particular chromosomal region in all of the multiple lesions from a single patient, the same allele was lost at each locus, without exception. Statistical analysis of these allele-specific losses strongly suggests that topologically distinct lesions are related and likely arise from a common precursor cell.
Asunto(s)
Transformación Celular Neoplásica/genética , Neoplasias Primarias Múltiples/genética , Neoplasias del Cuello Uterino/genética , Sondas de ADN de HPV , Progresión de la Enfermedad , Femenino , Humanos , Pérdida de Heterocigocidad , Repeticiones de Microsatélite , Neoplasias Primarias Múltiples/etiología , Neoplasias Primarias Múltiples/patología , Neoplasias Primarias Múltiples/virología , Papillomaviridae/clasificación , Papillomaviridae/genética , Papillomaviridae/aislamiento & purificación , Infecciones por Papillomavirus/complicaciones , Estudios Retrospectivos , Infecciones Tumorales por Virus/complicaciones , Displasia del Cuello del Útero/genética , Displasia del Cuello del Útero/patología , Displasia del Cuello del Útero/virología , Displasia del Cuello del Útero/etiología , Neoplasias del Cuello Uterino/etiología , Neoplasias del Cuello Uterino/patología , Neoplasias del Cuello Uterino/virologíaRESUMEN
Zinc is concentrated in the dorsal horn of the spinal cord and has been proposed to alter excitability of primary afferent C-fibers, structures believed to be important in nociceptive transmission. Based on the inhibitory effect of zinc on the activity of various other neurotransmitters that play a role in nociception, we tested the hypothesis that zinc modulates pain transmission. To test this, we examined the effect of exogenous zinc, administered intrathecally (i.t.), on nociception in the mouse. We also assessed the impact of decreased concentrations of endogenously occurring zinc in the extracellular fluid brought about by an i.t. injection of either ethylenediaminetetraacetic acid disodium-calcium salt (Ca++EDTA), a calcium-saturated, membrane-impermeable chelator of divalent cations, or of dipicolinic acid, a zinc chelator. Injection of zinc produced a dose-related antinociceptive effect, optimal at 90 min in the writhing assay, but had no effect on tail-flick response latencies. In contrast, injection of either Ca++EDTA or dipicolinic acid produced a dose-related hyperalgesia in the tail-flick assay at 90 min after injection. Responses induced in the writhing assay were unaffected by Ca++EDTA. Although zinc had no effect on thermal nociception, the hyperalgesic effect of Ca++EDTA was antagonized by coadministration of Ca++EDTA with zinc. Similarly, the antinociceptive effect of zinc on writhing responses was attenuated when coadministered with Ca++EDTA. Zinc also inhibited primary afferent C-fiber activity because 10 ng of zinc i.t. inhibited the behavioral response induced by injection i.t. of 1 nmol of capsaicin. Neither zinc nor Ca++EDTA altered writhing or tail-flick latencies, respectively, when injected intracerebroventricularly. These findings support the hypothesis that endogenous zinc, localized in the dorsal horn of the spinal cord, plays a role in the regulation of pain.
Asunto(s)
Quelantes/farmacología , Ácido Edético/farmacología , Dolor/fisiopatología , Ácidos Picolínicos/farmacología , Médula Espinal/fisiología , Zinc/fisiología , Analgésicos/farmacología , Animales , Masculino , Ratones , Zinc/farmacologíaRESUMEN
Nerve growth factor (NGF) induces a relatively long-term hyperalgesia in rats, whereas substance P (SP) N-terminal fragments, like SP(1-7), produce a long-lasting antinociception in mice. We used various nociceptive assays to compare the effects of these compounds on pain transmission when injected intrathecally (i.t.) in mice, and to determine whether either compound affects the action of the other. NGF produced thermal hyperalgesia when injected i.t. in mice 24 and 48 hr before testing by the tail-flick assay. During this same interval, NGF elicited no effect on the response to von Frey fibers or on chemically induced nociception measured by the writhing assay. In contrast to NGF, SP(1-7) had no effect on tail-flick latencies but induced antinociception in the writhing assay 24 hr after injection. When administered 2 hr before NGF, SP(1-7) antagonized the thermal hyperalgesic effect of NGF in a dose-related fashion, despite the inability of SP(1-7) to alter tail-flick latency when administered alone. NGF, in turn, antagonized the antinociceptive effects of SP(1-7) in the writhing assay. The D-amino acid-substituted analog, D-SP(1-7), failed to mimic the antinociceptive effect of SP(1-7) or to alter the hyperalgesic effect of NGF, which indicated a stereoselective action of SP(1-7). D-SP(1-7), that inhibits SP(1-7) binding, did reverse the ability of SP(1-7) to antagonize NGF-induced hyperalgesia, consistent with its action as a SP N-terminal antagonist. Mutual antagonism between NGF and SP may reflect modulatory roles of these endogenously occurring peptides during chronic pain when N-terminal metabolites of SP may accumulate.
Asunto(s)
Analgésicos/farmacología , Hiperalgesia/inducido químicamente , Factores de Crecimiento Nervioso/farmacología , Fragmentos de Péptidos/farmacología , Sustancia P/farmacología , Animales , Relación Dosis-Respuesta a Droga , Masculino , Ratones , Factores de Crecimiento Nervioso/antagonistas & inhibidoresRESUMEN
Substance P (SP) is released from primary afferent fibers in response to nociceptive stimuli. Capsaicin, which produces an initial hyperalgesic response followed by persistent antinociception, also elicits release of SP from primary afferent fibers. Capsaicin pretreatment decreases the content and release of SP from primary afferent fibers. This effect on SP has been hypothesized to mediate the antinociceptive effect of capsaicin. To test this hypothesis, mice were injected intrathecally (i.t.) with antinociceptive doses of capsaicin or SP(1-7) before superfusion of spinal cord tissue with 3 microM capsaicin 24, 48, 96 or 168 h later. N-terminal metabolic fragments of SP that accumulate after capsaicin-induced SP release and are involved in the antinociceptive effect of capsaicin, were also tested. Like capsaicin SP(1-3), SP(1-4) and SP(1-7) were each antinociceptive when injected 24 h before nociceptive testing. However, at this time there was no decrease in capsaicin-evoked release of SP in tissue from capsaicin- and SP(1-7)-pretreated animals compared to those injected with vehicle. In contrast, capsaicin-evoked SP release decreased significantly in tissue from mice pretreated with capsaicin or SP(1-7) 48 h prior to testing. D-Substance P(1-7), which prevents antinociception, blocked capsaicin- and SP(1-7)-induced decreases in SP release, indicating that these effects are mediated by SP N-terminal activity. Total spinal cord content of SP did not differ amongst treatment groups. These data indicate that antinociception does not appear to depend on decreases in SP release or content as antinociception precedes decreases in SP release.
Asunto(s)
Capsaicina/farmacología , Dolor/tratamiento farmacológico , Médula Espinal/efectos de los fármacos , Sustancia P/metabolismo , Animales , Evaluación Preclínica de Medicamentos , Inyecciones Espinales , Masculino , Ratones , Dolor/fisiopatología , Perfusión , Médula Espinal/metabolismoRESUMEN
((2S,3S)-[cis-2-(diphenylmethyl)-N-[(2-methoxyphenyl)-methyl]-1-az abicyclo[2.2.2]octan-3-amine]) (CP-96,345) noncompetitively inhibits substance P (SP) binding at the neurokinin-1 (NK-1) site and has been widely used to determine the extent of NK-1 activity in nociception. To test the selectivity of this compound in vivo regarding other putative nociceptive transmitters, such as excitatory amino acids, we compared the actions of CP-96,345 to those of ((2R,3R)-[cis-2-(diphenylmethyl)-N-[(2-methoxyphenyl)-methyl]-1-az abicyclo[2.2.2]octan-3-amine]), a less active isomer, on behavioral responses induced by SP, N-methyl-D-aspartate (NMDA) and kainic acid (KA) injected intrathecally in mice. When injected intrathecally, SP, NMDA or KA produce a caudally directed biting and scratching behavior that lasted for approximately 60 to 90 sec. At a dose as high as 2 nmol, CP-96,345 had no effect on responses induced by a single injection of 22.5 pmol of SP. In contrast, NMDA-induced behaviors were inhibited by CP-96,345 in a dose-related fashion beginning at a dose as low as 0.02 nmol. There was also an inhibitory effect of CP-96,345 on KA-induced activity that was not dose related. The more potent inhibitor of [3H] SP binding, (+)-(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine (CP-99,994), was approximately 10 times more potent in inhibiting NMDA-induced activity than CP-96,345. CP-99,994 also inhibited NMDA-induced activity at doses that failed to inhibit SP-induced behavior. Also attenuated by CP-96,345 was the development of sensitization to the behavioral effects produced by repeated injections of KA and desensitization to repeated injections of SP, phenomena linked to an action of the N-terminus of SP. NMDA-induced behaviors and sensitization to KA were found to be sensitive to verapamil, consistent with their mediation by calcium. These results indicate that either CP-96,345 and CP-99,994 do not inhibit NK-1-induced activity in the mouse spinal cord, or that exogenously administered SP does not induce behavioral responses by an interaction with NK-1 receptors. Whether CP-96,345 acts by a mechanism that involves inhibition of calcium channels and/or SP N-terminal activity requires further testing.