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399 Early cytokine expression in mouse sciatic nerve after chronic constriction nerve injury depends on calpain
Poster Presentations / Animal studies – Systems / European Journal of Pain 11(S1) (2007) S59–S207
S177
cord by nerve injury using microarray techniques. Peripheral benzodiazepine receptor (PBR) mRNA was found to be up-regulated in the spinal cord of mice with spinal nerve injury as compared with sham operated mice. Up-regulation of PBR mRNA by peripheral nerve injury has also been reported in dorsal root ganglion neurons (Xiao et al., 2002; Karchewski et al., 2004) and implicated its role in sensory axon regeneration (Mills et al., 2005). PBR has been named to distinguish it from the central benzodiazepine receptor, which is the component of the GABAA receptor. PBR functions as a cholesterol transporter which delivers cholesterol to CYP11A1 in the inner mitochondrial membrane. This is the initial step of neurosteroid synthesis. Interestingly, neurosteorid synthesized then facilitates the activation (at a lower concentration) of and directly activates (at a higher concentration) GABAA receptor. It has been shown recently that the increase in intracellular chloride concentration in spinal neurons caused by the reduction of potassium-chloride co-transporter KCC2 expression in the neuropathic pain state has converted the inhibitory outcome of GABAA receptor activation to the excitatory one (Coull et al., 2003, 2005). In the present study, we have tested whether enhanced neurosteroid synthesis is responsible for the activation of GABAA receptor leading to neuropathic pain in nerve injured mice and found it is the case.
CCI the cytokine expression was investigated in ipsiand contralateral sciatic nerves and dorsal root ganglia (DRG). Possible upstream regulatory mechanisms were studied with inhibitors to the N-methyl-D-aspartate (NMDA) receptor ((+)-MK-801) and to calpain (MDL-28170). Results. TNF, IL-1b and IL-10 mRNA levels increased as early as 1 h after CCI ipsilaterally in the sciatic nerve. MDL-28170, but not (+)-MK-801 inhibited TNF and IL-1b upregulation 1 h after CCI. Conclusion. Calpain may be one of the earliest mediators of cytokine upregulation after peripheral nerve injury. The calpain system might be a promising target for neuro- and algo-protective agents.
doi:10.1016/j.ejpain.2007.03.413
In the present study, we examined the effects of spinal administration of gabapentin on rat dorsal horn neuron activity following spinal nerve ligation (SNL) at various time points post-operation (PO). Wide-dynamic-range (WDR) neurons, but not the high-threshold (HT) neurons, showed a significant increase in spontaneous activity following SNL compared to sham controls at PO day 7–14, but not PO day >21. The proportion of neurons responding to non-noxious mechanical stimulation of the hind paw significantly increased at PO day >21, but stimulus-response functions to graded mechanical stimulation remained unchanged. Spinal administration of gabapentin dose-dependently inhibited WDR neuron responses to mechanical stimulation at PO day >21 (IC50 = 30.94 mM), but had no effect on sham controls (100 mM). The inhibitory effect of gabapentin (100 mM) on spinal neuron responses was correlated with time PO, such that at PO day >21 gabapentin produced maximum efficacy by inhibiting responses to 35.11 ± 8% of control. These results demonstrate that gabapentin directly inhibits spinal mechanosensory neuron activity following peripheral neuropathy through a spinal mechanism of action. The inhibitory action of gabapentin on spinal mechanosensory neurons is consistent with its antinociceptive effects in preclinical behavioral models of neuropathic pain.
399 EARLY CYTOKINE EXPRESSION IN MOUSE SCIATIC NERVE AFTER CHRONIC CONSTRICTION NERVE INJURY DEPENDS ON CALPAIN N. Ueceyler *, A. Tscharke, C. Sommer Department of Neurology, University of Wuerzburg, Germany Background and aims. Peripheral nerve injury leads to Wallerian degeneration with subsequent alterations in cytokine expression that may contribute to the development of neuropathic pain. Here we set out to characterize the very early temporal pattern of cytokine regulation after chronic constriction nerve injury (CCI) in mice. Animals and methods. One hundred and forty mice of C57Bl/6J background were investigated after CCI of the right sciatic nerve. The relative mRNA expression of the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF) and interleukin-1beta (IL-1b) and of the anti-inflammatory cytokines IL-4 and IL-10 were measured with quantitative real-time PCR (qRTPCR). 1, 3, 6, 9, 12, 24 h, and 3 and 7 days after
doi:10.1016/j.ejpain.2007.03.414
400 DIRECT INHIBITORY EFFECTS OF GABAPENTIN ON SPINAL MECHANOSENSORY NEURONS FOLLOWING PERIPHERAL NEUROPATHY IN THE RAT K.-C. Choong, A. Liang, M.O. Urban * Pain Research, Merck Research Laboratories, West Point, PA, USA
S177
cord by nerve injury using microarray techniques. Peripheral benzodiazepine receptor (PBR) mRNA was found to be up-regulated in the spinal cord of mice with spinal nerve injury as compared with sham operated mice. Up-regulation of PBR mRNA by peripheral nerve injury has also been reported in dorsal root ganglion neurons (Xiao et al., 2002; Karchewski et al., 2004) and implicated its role in sensory axon regeneration (Mills et al., 2005). PBR has been named to distinguish it from the central benzodiazepine receptor, which is the component of the GABAA receptor. PBR functions as a cholesterol transporter which delivers cholesterol to CYP11A1 in the inner mitochondrial membrane. This is the initial step of neurosteroid synthesis. Interestingly, neurosteorid synthesized then facilitates the activation (at a lower concentration) of and directly activates (at a higher concentration) GABAA receptor. It has been shown recently that the increase in intracellular chloride concentration in spinal neurons caused by the reduction of potassium-chloride co-transporter KCC2 expression in the neuropathic pain state has converted the inhibitory outcome of GABAA receptor activation to the excitatory one (Coull et al., 2003, 2005). In the present study, we have tested whether enhanced neurosteroid synthesis is responsible for the activation of GABAA receptor leading to neuropathic pain in nerve injured mice and found it is the case.
CCI the cytokine expression was investigated in ipsiand contralateral sciatic nerves and dorsal root ganglia (DRG). Possible upstream regulatory mechanisms were studied with inhibitors to the N-methyl-D-aspartate (NMDA) receptor ((+)-MK-801) and to calpain (MDL-28170). Results. TNF, IL-1b and IL-10 mRNA levels increased as early as 1 h after CCI ipsilaterally in the sciatic nerve. MDL-28170, but not (+)-MK-801 inhibited TNF and IL-1b upregulation 1 h after CCI. Conclusion. Calpain may be one of the earliest mediators of cytokine upregulation after peripheral nerve injury. The calpain system might be a promising target for neuro- and algo-protective agents.
doi:10.1016/j.ejpain.2007.03.413
In the present study, we examined the effects of spinal administration of gabapentin on rat dorsal horn neuron activity following spinal nerve ligation (SNL) at various time points post-operation (PO). Wide-dynamic-range (WDR) neurons, but not the high-threshold (HT) neurons, showed a significant increase in spontaneous activity following SNL compared to sham controls at PO day 7–14, but not PO day >21. The proportion of neurons responding to non-noxious mechanical stimulation of the hind paw significantly increased at PO day >21, but stimulus-response functions to graded mechanical stimulation remained unchanged. Spinal administration of gabapentin dose-dependently inhibited WDR neuron responses to mechanical stimulation at PO day >21 (IC50 = 30.94 mM), but had no effect on sham controls (100 mM). The inhibitory effect of gabapentin (100 mM) on spinal neuron responses was correlated with time PO, such that at PO day >21 gabapentin produced maximum efficacy by inhibiting responses to 35.11 ± 8% of control. These results demonstrate that gabapentin directly inhibits spinal mechanosensory neuron activity following peripheral neuropathy through a spinal mechanism of action. The inhibitory action of gabapentin on spinal mechanosensory neurons is consistent with its antinociceptive effects in preclinical behavioral models of neuropathic pain.
399 EARLY CYTOKINE EXPRESSION IN MOUSE SCIATIC NERVE AFTER CHRONIC CONSTRICTION NERVE INJURY DEPENDS ON CALPAIN N. Ueceyler *, A. Tscharke, C. Sommer Department of Neurology, University of Wuerzburg, Germany Background and aims. Peripheral nerve injury leads to Wallerian degeneration with subsequent alterations in cytokine expression that may contribute to the development of neuropathic pain. Here we set out to characterize the very early temporal pattern of cytokine regulation after chronic constriction nerve injury (CCI) in mice. Animals and methods. One hundred and forty mice of C57Bl/6J background were investigated after CCI of the right sciatic nerve. The relative mRNA expression of the pro-inflammatory cytokines tumor necrosis factor-alpha (TNF) and interleukin-1beta (IL-1b) and of the anti-inflammatory cytokines IL-4 and IL-10 were measured with quantitative real-time PCR (qRTPCR). 1, 3, 6, 9, 12, 24 h, and 3 and 7 days after
doi:10.1016/j.ejpain.2007.03.414
400 DIRECT INHIBITORY EFFECTS OF GABAPENTIN ON SPINAL MECHANOSENSORY NEURONS FOLLOWING PERIPHERAL NEUROPATHY IN THE RAT K.-C. Choong, A. Liang, M.O. Urban * Pain Research, Merck Research Laboratories, West Point, PA, USA