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1.
J Neurosci ; 32(34): 11890-6, 2012 Aug 22.
Artículo en Inglés | MEDLINE | ID: mdl-22915129

RESUMEN

Evidence suggesting the involvement of P2X2 and P2X3 in chronic pain has been obtained mostly from rodent models. Here we show that rodents may be poor predictors of P2X3 pharmacology in human. We demonstrate that monkey and human dorsal root ganglion (DRG) neurons do not express appreciable levels of P2X2 subunit, contrary to rat sensory neurons. Additionally, we report functional P2X3 activity in monkey DRG neurons and confirm the absence of functional P2X2/3 receptors. Interestingly, native P2X3 receptors in rat and monkey DRGs show similar agonist potency, but different antagonist potencies for TNP-ATP [2-O-(2,4,6-trinitrophenyl)-ATP] and RO51. This unexpected difference in antagonist potency was confirmed by comparing rat and human P2X3 receptors in HEK293 cells. Mutagenesis studies reveal that two extracellular residues, A197 and T202, are synergistically responsible for the potency drop in primate P2X3 receptors. These results uncover species-specific P2X3 pharmacology and identify key mechanisms impacting the translatability of potential analgesics targeting P2X3 receptors.


Asunto(s)
Expresión Génica/fisiología , Agonistas del Receptor Purinérgico P2X/farmacología , Antagonistas del Receptor Purinérgico P2X/farmacología , Receptores Purinérgicos P2X/metabolismo , Células Receptoras Sensoriales/efectos de los fármacos , Células Receptoras Sensoriales/metabolismo , Adenosina Trifosfato/análogos & derivados , Adenosina Trifosfato/farmacología , Adulto , Análisis de Varianza , Animales , Recuento de Células , Células Cultivadas , Niño , Relación Dosis-Respuesta a Droga , Estimulación Eléctrica , Femenino , Ganglios Espinales/citología , Expresión Génica/efectos de los fármacos , Humanos , Macaca fascicularis , Masculino , Potenciales de la Membrana/efectos de los fármacos , Potenciales de la Membrana/fisiología , Persona de Mediana Edad , Mutagénesis/genética , Técnicas de Placa-Clamp , Pirimidinas/farmacología , Ratas , Ratas Sprague-Dawley , Receptores Purinérgicos P2X/genética , Especificidad de la Especie , Transfección , Adulto Joven
2.
Pain ; 152(12): 2852-2860, 2011 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-22018972

RESUMEN

The role of muscarinic receptor subtype-1 (M1) in chronic pain is unclear. In an attempt to gain an understanding of its role, we have tested xanomeline, an M1/M4-preferring agonist, together with nonselective (scopolamine and pirenzepine), and selective (MT-7 and MT-3) muscarinic receptor (M1 and M4, respectively) antagonists in a number of inflammatory and neuropathic pain models. Xanomeline potently and effectively reversed tactile allodynia and heat hyperalgesia associated with established neuropathic and inflammatory pain in both rat and mouse models. Scopolamine and pirenzepine completely blocked the analgesic response to xanomeline, confirming that the analgesic effect is mediated by the muscarinic system. The highly selective M1 receptor toxin, MT-7, almost completely abolished the analgesic response to xanomeline when administered supraspinally. However, the highly selective M4 receptor toxin, MT-3, only marginally reversed the analgesia when given supraspinally, and had no effect when given spinally. In conclusion, the data presented show that the nonselective muscarinic agonist xanomeline is analgesic in models of persistent pain and suggest that the activation of supraspinal M1 receptors, and to a lesser extent supraspinal M4 receptors, contributes to that analgesia.


Asunto(s)
Analgésicos/farmacología , Dolor Crónico/metabolismo , Agonistas Muscarínicos/farmacología , Neuralgia/metabolismo , Piridinas/farmacología , Receptor Muscarínico M1/agonistas , Receptor Muscarínico M4/agonistas , Tiadiazoles/farmacología , Animales , Células CHO , Sistema Nervioso Central/efectos de los fármacos , Sistema Nervioso Central/metabolismo , Sistema Nervioso Central/patología , Dolor Crónico/tratamiento farmacológico , Dolor Crónico/patología , Cricetinae , Cricetulus , Modelos Animales de Enfermedad , Masculino , Ratones , Ratones Endogámicos C57BL , Neuralgia/tratamiento farmacológico , Neuralgia/patología , Ratas , Ratas Sprague-Dawley , Receptor Muscarínico M1/genética , Receptor Muscarínico M1/metabolismo , Receptor Muscarínico M4/genética , Receptor Muscarínico M4/metabolismo
3.
Mol Pain ; 6: 90, 2010 Dec 10.
Artículo en Inglés | MEDLINE | ID: mdl-21143971

RESUMEN

BACKGROUND: The CCR2/CCL2 system has been identified as a regulator in the pathogenesis of neuropathy-induced pain. However, CCR2 target validation in analgesia and the mechanism underlying antinociception produced by CCR2 antagonists remains poorly understood. In this study, in vitro and in vivo pharmacological approaches using a novel CCR2 antagonist, AZ889, strengthened the hypothesis of a CCR2 contribution to neuropathic pain and provided confidence over the possibilities to treat neuropathic pain with CCR2 antagonists. RESULTS: We provided evidence that dorsal root ganglia (DRG) cells harvested from CCI animals responded to stimulation by CCL2 with a concentration-dependent calcium rise involving PLC-dependent internal stores. This response was associated with an increase in evoked neuronal action potentials suggesting these cells were sensitive to CCR2 signalling. Importantly, treatment with AZ889 abolished CCL2-evoked excitation confirming that this activity is CCR2-mediated. Neuronal and non-neuronal cells in the spinal cord were also excited by CCL2 applications indicating an important role of spinal CCR2 in neuropathic pain. We next showed that in vivo spinal intrathecal injection of AZ889 produced dose-dependent analgesia in CCI rats. Additionally, application of AZ889 to the exposed spinal cord inhibited evoked neuronal activity and confirmed that CCR2-mediated analgesia involved predominantly the spinal cord. Furthermore, AZ889 abolished NMDA-dependent wind-up of spinal withdrawal reflex pathway in neuropathic animals giving insight into the spinal mechanism underlying the analgesic properties of AZ889. CONCLUSIONS: Overall, this study strengthens the important role of CCR2 in neuropathic pain and highlights feasibility that interfering on this mechanism at the spinal level with a selective antagonist can provide new analgesia opportunities.


Asunto(s)
Hiperalgesia/tratamiento farmacológico , Neuralgia/tratamiento farmacológico , Piperazinas/uso terapéutico , Receptores CCR2/antagonistas & inhibidores , Médula Espinal/patología , Animales , Señalización del Calcio , Sistemas de Liberación de Medicamentos , Ganglios Espinales/patología , Piperazinas/farmacología , Ratas , Ratas Sprague-Dawley , Receptores CCR2/fisiología , Transducción de Señal
4.
Pain ; 151(2): 337-344, 2010 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-20696525

RESUMEN

Cannabinoids are analgesic in man, but their use is limited by their psychoactive properties. One way to avoid cannabinoid receptor subtype 1 (CB1R)-mediated central side-effects is to develop CB1R agonists with limited CNS penetration. Activation of peripheral CB1Rs has been proposed to be analgesic, but the relative contribution of peripheral CB1Rs to the analgesic effects of systemic cannabinoids remains unclear. Here we addressed this by exploring the analgesic properties and site of action of AZ11713908, a peripherally restricted CB1R agonist, in rodent pain models. Systemic administration of AZ11713908 produced robust efficacy in rat pain models, comparable to that produced by WIN 55, 212-2, a CNS-penetrant, mixed CB1R and CB2R agonist, but AZ11713908 generated fewer CNS side-effects than WIN 55, 212-in a rat Irwin test. Since AZ11713908 is also a CB2R inverse agonist in rat and a partial CB2R agonist in mouse, we tested the specificity of the effects in CB1R and CB2R knock-out (KO) mice. Analgesic effects produced by AZ11713908 in wild-type mice with Freund's complete adjuvant-induced inflammation of the tail were completely absent in CB1R KO mice, but fully preserved in CB2R KO mice. An in vivo electrophysiological assay showed that the major site of action of AZ11713908 was peripheral. Similarly, intraplantar AZ11713908 was also sufficient to induce robust analgesia. These results demonstrate that systemic administration of AZ11713908, produced robust analgesia in rodent pain models via peripheral CB1R. Peripherally restricted CB1R agonists provide an interesting novel approach to analgesic therapy for chronic pain.


Asunto(s)
Antiinflamatorios no Esteroideos/uso terapéutico , Cannabinoides/uso terapéutico , Inflamación/tratamiento farmacológico , Neuralgia/tratamiento farmacológico , Receptor Cannabinoide CB1/metabolismo , Animales , Bencimidazoles/uso terapéutico , Benzoxazinas/sangre , Benzoxazinas/uso terapéutico , Bloqueadores de los Canales de Calcio/sangre , Bloqueadores de los Canales de Calcio/uso terapéutico , Carragenina/efectos adversos , Modelos Animales de Enfermedad , Relación Dosis-Respuesta a Droga , Adyuvante de Freund/efectos adversos , Humanos , Inflamación/inducido químicamente , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Morfolinas/sangre , Morfolinas/uso terapéutico , Naftalenos/sangre , Naftalenos/uso terapéutico , Neuralgia/inducido químicamente , Dimensión del Dolor/métodos , Ratas , Ratas Sprague-Dawley , Receptor Cannabinoide CB1/deficiencia , Receptor Cannabinoide CB2/deficiencia , Sulfonamidas/uso terapéutico , Factores de Tiempo
5.
Pain ; 104(3): 609-616, 2003 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-12927633

RESUMEN

Although the neuropeptide neuromedin U (NMU) was first isolated from the spinal cord, its actions in this site are unknown. The recent identification of the NMU receptor subtype 2 (NMU2R) in the spinal cord has increased the interest in investigating the role of NMU in this part of the central nervous system. Here, we report a novel function for NMU in spinal nociception in the mouse. Systemic perfusion of NMU (rat, NMU-23) dose-dependently (0.2, 0.5, 1, and 2.5 microM) potentiated both the background activity and noxious pinch-evoked response of nociceptive or wide dynamic range, but not non-nociceptive, dorsal horn neurons. At 2.5 microM, NMU-23 increased the total background activity from 154+/-34 to 1374+/-260 spikes/160 s (P<0.005, n=28) and increased the evoked nociceptive response by 185+/-50% (P<0.01, n=13). Intrathecal administration of NMU-23 (0.4, 1.1, and 3.8 nmol/10 microl) dose-dependently decreased thermal withdrawal latencies and produced a morphine-sensitive behavioral response. These electrophysiological and behavioral results suggest that NMU may be a novel physiological regulator in spinal nociceptive transmission and processing.


Asunto(s)
Proteínas de la Membrana , Neuropéptidos/toxicidad , Dimensión del Dolor/efectos de los fármacos , Dolor/inducido químicamente , Potenciales de Acción/efectos de los fármacos , Potenciales de Acción/fisiología , Animales , Relación Dosis-Respuesta a Droga , Masculino , Ratones , Dolor/fisiopatología , Dimensión del Dolor/métodos , Células del Asta Posterior/efectos de los fármacos , Células del Asta Posterior/fisiología , Ratas , Receptores de Neurotransmisores/agonistas , Receptores de Neurotransmisores/fisiología
6.
J Med Chem ; 45(11): 2160-72, 2002 May 23.
Artículo en Inglés | MEDLINE | ID: mdl-12014954

RESUMEN

The 1-(2-nitrophenyl)thiosemicarbazide (TSC) derivative, (S)-1-[4-(4-benzhydrylthiosemicarbazido)-3-nitrobenzenesulfonyl]pyrrolidine-2-carboxylic acid [2-[(2-dimethylaminoethyl)methylamino]ethyl]amide (bradyzide; (S)-4), was recently disclosed as a novel, potent, orally active nonpeptide bradykinin (BK) B2 receptor antagonist. The compound inhibited the specific binding of [3H]BK to NG108-15 cell membrane preparations (rodent neuroblastoma-glioma) expressing B2 receptors with a K(i) of 0.5 +/- 0.2 nM. Compound (S)-4 also demonstrated oral efficacy against Freund's complete adjuvant (FCA)-induced mechanical hyperalgesia in rats with an ED50 value of 0.84 micromol/kg. After we optimized the terminal binding determinants projecting from the TSC framework, we found that it was possible to replace the potentially toxicophoric nitro and divalent sulfur moieties with only a 15-fold loss in binding affinity ((S)-14a). However, bradyzide and its congeners were found to have much lower affinities for cloned human B2 receptors, expressed in Cos-7 cells. The hitherto synthesized TSC series was screened against the human B2 receptor, and the dibenzosuberane (DBS) pharmacophore emerged as the key structural requirement for potency. Incorporation of this group resulted in a series of derivatives ((S)-14d,e and 19b-d) with K(i) ranges of 10.7-176 nM in NG108-15 cells (expressing the rodent B2 receptor) and 0.79-253 nM in Cos-7 cells (expressing the human B2 receptor). There was no evidence of agonist activity with any of the nonpeptides in any of the cell lines tested. In vivo, oral administration of compound 19c reversed FCA-induced and turpentine-induced mechanical hyperalgesia in rodents with ED50 values of 0.027 and 0.32 micromol/kg, respectively. The selectivity profiles of compounds (S)-14f and (S)-14g were also assessed to determine the conformational and/or steric preferences of the double-ring arrangement. The affinity of (S)-14 g for the human B2 receptor suggested that it may be a hydrophobic interaction with the ethane bridge of the DBS moiety that accounts for the increased potency of compounds (S)-14d,e and 19b,c at this receptor, by favoring a binding mode inaccessible to the unsubstituted diphenylmethyl derivative, (S)-4.


Asunto(s)
Antiinflamatorios no Esteroideos/síntesis química , Antagonistas de los Receptores de Bradiquinina , Pirrolidinas/síntesis química , Tiosemicarbazonas/síntesis química , Administración Oral , Animales , Antiinflamatorios no Esteroideos/química , Antiinflamatorios no Esteroideos/farmacología , Artritis Experimental/tratamiento farmacológico , Línea Celular , Femenino , Humanos , Hiperalgesia/inducido químicamente , Hiperalgesia/tratamiento farmacológico , Modelos Moleculares , Estimulación Física , Pirrolidinas/química , Pirrolidinas/farmacología , Ensayo de Unión Radioligante , Ratas , Ratas Sprague-Dawley , Receptor de Bradiquinina B2 , Especificidad de la Especie , Relación Estructura-Actividad , Tiosemicarbazonas/química , Tiosemicarbazonas/farmacología , Trementina
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