RESUMO
Objective:To investigate the effect of lappaconitine (LA) on neuropathic pain (NPP) mediated by retrograde transport of purinergic P2X3 receptor (P2X3R) in dorsal root ganglion (DRG) neurons of rats with chronic constriction injury (CCI) of the sciatic nerve.Methods:Seventy-two male healthy SD rats were selected to construct the NPP model following CCI of the sciatic nerve by ligating the right sciatic nerve. according to the random number table method. The rats were divided into CCI group, CCI+LA group and normal control group according to the random number table method, with 24 rats in each group. In normal control group, the right sciatic nerve was exposed without ligation. In CCI+LA group, the rats were given 2 g/L LA (ie, 4 mg/kg intravenously for once a day for one day only) after the same treatment as CCI group. Other two groups were injected with the identical amount of normal saline in the same way. The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were evaluated before injury and at 2, 6, 12 and 24 hours after injury to evaluate the symptoms of neuralgia caused by nerve injury. The proximal and distal nerve fragments were collected in the three groups at 2, 6, 12 and 24 hours after injury. Western blotting was applied to analyze the expression of P2X3R at 2, 6, 12 and 24 hours after injury and the expression of neurotrophic factor (NGF) and tyrosine kinase receptor A (TrkA) at 24 hours after injury to evaluate the effect of LA on P2X3R, NGF and TrkA.Results:There were insignificant differences in MWT and TWL among all groups before injury (all P>0.05). Compared with normal control group, MWT and TWL were significantly decreased in CCI group and CCI+LA group at 2, 6, 12 and 24 hours after injury (all P<0.05 or 0.01). There were insignificant differences in MWT and TWL between CCI group and CCI+LA group at 2 and 6 hours after injury (all P>0.05), while MWT and TWL were significantly higher in CCI+LA group than those in CCI group at 12 and 24 hours after injury (all P<0.05 or 0.01). In the proximal sciatic nerve segment, Western blotting showed similar levels of P2X3R among all groups at 2, 6, 12 and 24 hours after injury (all P>0.05). In the distal sciatic nerve segment, Western blotting showed higher expression of P2X3R in CCI group than that in normal control group at 2, 6, 12, 24 hours after injury (all P<0.01), higher expression of P2X3R in CCI+LA group than that in normal control group at 2, 6 and 12 hours after injury (all P<0.05), similar expression of P2X3R expression between CCI+LA group and normal control group at 24 hours after injury ( P>0.05), similar expression of P2X3R between CCI group and CCI+LA group at 2 and 6 hours after injury (all P>0.05), and lower expression of P2X3R in CCI+LA group than that in CCI group at 12 and 24 hours after injury ( P<0.05 or 0.01). In the proximal and distal nerve fragments, the expression of NGF was lower in normal control group than that in CCI group and CCI+LA group ( P<0.05 or 0.01), but was similar between CCI group and CCI+LA group at 24 hours after injury ( P>0.05). In the proximal and distal nerve fragments, there were insignificant differences in the expression of TrkA among all groups at 24 hours after injury (all P>0.05). Conclusion:Early LA treatment after injury can alleviate mechanical and thermal hyperalgesia in NPP rats, which may be related to the reduction of P2X3R retrograde transport in DRG neuron axonal.
RESUMO
Objective: To observe the therapeutic effect of mild moxibustion on irritable bowel syndrome (IBS) visceral hyperalgesiamodel rats and its regulatory effect on P2X3 receptors in the spinal cord, anterior cingutate cortex (ACC) and thalamic ventral posterolateral nucleus (VPL). Methods: Thirty 8-day-old newborn rats were randomly divided into a normal group (n=6) and a modeling group (n=24) according to the completely random number table method. Rats in the normal group were bred routinely, and those in the modeling group were subjected to preparing IBS chronic visceral hyperalgesia model using colorectal distention (CRD) in stimulation method. Rats successfully modelled were re-divided into a model group, a mild moxibustion group, a P2X3 receptor antagonist group, and a normal saline group according to the completely random number table method with 6 rats in each group. Rats in each group received corresponding interventions from the 37-day old, once a day for 7 consecutive days. Immunohistochemistry and Western blot assays were used to detect P2X3 protein expressions in the spinal cord, ACC and VPL of rats. Results: Under different intensities of CRD stimulation, the abdominal withdrawal reflex (AWR) scores of the model group were significantly increased versus the normal group (all P<0.05); the AWR scores of the mild moxibustion group and the P2X3 receptor antagonist group were significantly reduced versus the model group (all P<0.01). The P2X3 protein expressions in rat spinal cord, ACC and VPL tissues of the model group were significantly increased versus the normal group (all P<0.01); the P2X3 protein expressions in rat spinal cord, ACC and VPL tissues of the mild moxibustion group and the P2X3 receptor antagonist group were significantly reduced versus the model group (all P<0.01). Conclusion: Mild moxibustion can inhibit the P2X3 receptor expressions in the spinal cord, ACC, and VPL tissues of IBS visceral hyperalgesia model rats, which may be the mechanism of mild moxibustion in relieving the central sensitization of rats with IBS visceral hyperalgesia.
RESUMO
Recently, we reported that astrocytes in the trigeminal caudal nucleus (Vc) of the brain stem express a purinergic receptor P2X₃, which is involved in the craniofacial pathologic pain. Although we observed protein expression of P2X₃ receptors (P2X₃ Rs) in the astrocyte of the Vc, it is still unclear that astrocyte has functional P2X₃Rs in Vc. To address this issue, we recorded asrtocytic P2X₃Rs by using whole cell voltage-clamp recording in the Vc of the GFAP-GFP mice, which was used as a guide to astrocytes with green fluorescence. While measuring voltage ramp-induced astrocytic membrane current, we found the amplitude of the current was increased when we applied P2-purinoreceptor agonist, α,β-meATP. This increase was blocked by co-application of A317491, P2X₃R antagonist. These results demonstrate that astrocytes in the Vc express functional P2X₃Rs, which might be critical in craniofacial pathologic pain.