Electroacupuncture at He-Mu points reduces P2X 4 receptor expression in visceral hypersensitivity***

Electroacupuncture at Shangjuxu (ST37) and Tianshu (ST25) was reported to improve visceral hypersensitivity in rats.Colorectal distension was utilized to generate a rat model of chronic visceral hypersensitivity in irritable bowel syndrome.Results showed that abdominal withdrawal reflex scores noticeably increased after model establishment.Simultaneously,P2X 4 receptor immunoreactivity significantly increased in the colon and spinal cord.Electroacupuncture and pinaverium bromide therapy both markedly decreased abdominal withdrawal reflex scores in rats with visceral hypersensitivity,and significantly decreased P2X 4 receptor immunoreactivity in the colon and spinal cord.These data suggest that electroacupuncture treatment can improve visceral hypersensitivity in rats with irritable bowel syndrome by diminishing P2X 4 receptor immunoreactivity in the colon and spinal cord.     

Effects of oxymatrine on sympathoexcitatory reflex induced by myocardial ischemic signaling mediated by P2X₃ receptors in rat SCG and DRG

Sympathoexcitatory reflex is characterized by an increase in blood pressure and sympathetic nerve activity. P2X₃ receptors in SCG neurons are involved in increasing sympathoexcitatory reflex after myocardial ischemic (MI) injury. The present study is aimed to explore the effects of oxymatrine (Oxy) on the transmission of myocardial ischemic signaling mediated by P2X₃ receptors in rat superior cervical ganglia (SCG) and cervical dorsal root ganglia (DRG) in the sympathoexcitatory reflex after myocardial ischemic injury. In this study, the expression levels of P2X₃ immunoreactivity, mRNA and protein were analyzed in SCG and DRG neurons by immunohistochemistry, in situ hybridization and Western blotting. The results show that the myocardial ischemic injury induces the increase of the systolic blood pressure and heart rate and upregulates the expression of P2X₃ receptors in SCG and DRG neurons. Upregulated expression of P2X₃ receptors in SCG and DRG neurons subsequently leads to the aggravated sympathoexcitatory reflex. Oxymatrine reduces the systolic blood pressure and heart rate in myocardial ischemic rats. After myocardial ischemic rats are treated with oxymatrine, the expression levels of P2X₃ immunoreactivity, mRNA and protein are lower than those in myocardial ischemic rats. Oxymatrine may decrease the expression of P2X₃ receptor and depress the aggravated sympathoexcitatory reflex induced by the nociceptive transmission of myocardial ischemic injury via P2X₃ receptors of rat SCG and DRG neurons.     

Effect of emodin on neuropathic pain transmission mediated by P2X2/3 receptor of primary sensory neurons

Neuropathic pain is the most difficult type of pain to cure. The P2X_2/3 receptors play a crucial role in facilitating the transmission of pain at neuropathic pain states. Emodin is a natural anthraquinone in rhubarb. The present research investigated the effects of emodin on the pain transmission in neuropathic pain states that was mediated by P2X_2/3 receptor in primary sensory neurons. Chronic constriction injury (CCI) model was used as neuropathic pain model. Emodin was dissolved in 0.5% sodium carboxymethyl cellulose (CMC) as vehicle. Sprague-Dawley male rats had been randomly divided into Sham + vehicle group, CCI + emodin group, and CCI + vehicle group. Mechanical withdrawal threshold and thermal withdrawal latency were measured. P2X_2/3 expression in L4/L5 dorsal root ganglion (DRG) was detected by immunohistochemistry, in situ hybridization (ISH) and RT-PCR. The mechanical withdrawal threshold and thermal withdrawal latency in CCI + vehicle group were lower than those in Sham + vehicle group and CCI + emodin group (p < 0.05), while P2X₂ and P2X₃ receptor expression of L4/L5 DRG in CCI + vehicle group was higher than those in the other two groups (p < 0.05). The co-local staining of P2X₂ and P2X₃ in the DRG of CCI group appeared to be more intense than that in the DRG of the other two groups with double-label fluorescence immunohistochemistry. The results showed that the application of emodin alleviated the hyperalgesia of CCI rats and significantly decreased the P2X_2/3 expression of L4/L5 DRG in CCI + emodin group compared with that in CCI + vehicle group (p < 0.05). The data of ISH and RT-PCR in P2X₂ and P2X₃ mRNA expression suggest that the pharmacologic mechanism of emodin is involved in the nucleic acid level. The results showed that emodin can inhibit the transmission of neuropathic pain mediated by P2X_2/3 receptor of primary sensory neurons to alleviate chronic neuropathic pain.     

VEGF and its receptor-2 involved in neuropathic pain transmission mediated by P2X2/3 receptor of primary sensory neurons

The pathogenesis of neuropathic pain is complex. P2X_2/3 receptor plays a crucial role in nociception transduction of chronic pain. VEGF inhibitors are effective for pain relief. The present study investigated the effects of VEGF and VEGF receptor-2 (VEGFR2) on the pain transmission in neuropathic pain states that mediated by P2X_2/3 receptor in primary sensory neurons. Chronic constriction injury (CCI) model was used as neuropathic pain model. Sprague-Dawley rats had been randomly divided into sham group, CCI group and CCI rats treated with anti-rVEGF antibody group. Mechanical withdrawal threshold and thermal withdrawal latency were measured. Expressions of VEGF, VEGFR2 and P2X_2/3 in L4-6 dorsal root ganglia (DRG) were detected by immunohistochemistry, RT-PCR and western blot analysis. The mechanical withdrawal threshold and thermal withdrawal latency in CCI group were lower than those in sham group and CCI rats treated with anti-rVEGF antibody group (p < 0.05), while VEGF, VEGFR2 and P2X_2/3 receptors’ expressions of L4-6 DRG in CCI group were higher than those in the other two groups (p < 0.05). The expressions of VEGF, VEGFR2 and P2X_2/3 in L4-6 DRG of CCI rats treated with anti-rVEGF antibody group were decreased compared with those in CCI group (p < 0.05). The results show that VEGF and VEGFR2 are involved in the pathogenesis of neuropathic pain and VEGF primarily potentiates pain responses mediated by P2X_2/3 receptor on DRG neurons. Anti-rVEGF treatment in CCI rats may alleviate chronic neuropathic pain by decreasing the expressions of VEGFR2 and P2X_2/3 receptors on DRG neurons to inhibit the transmission of neuropathic pain signaling.     

Effect of tetramethylpyrazine on primary afferent transmission mediated by P2X3 receptor in neuropathic pain states

Neuropathic pain is the most difficult type of pain to treat. The P2X₃ receptors play a crucial role in facilitating pain transmission at peripheral and spinal sites. The present research investigated the effects of tetramethylpyrazine (TMP) on the primary afferent transmission induced by P2X₃ receptor in neuropathic pain states. Chronic constriction injury (CCI) model was adopted. Sprague–Dawley male rats (n = 30) had been randomly divided into normal saline (sham + NS) group (I), TMP group (II), sham group (III), CCI + TMP group (IV), and CCI group (V). Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured and P2X₃ immunoreactivity in L4/L5 dorsal root ganglion (DRG) and spinal cord was detected by immunohistochemistry. The mechanical withdrawal threshold and thermal withdrawal latency in group V were lower than those in groups I–III or IV (p < 0.05), while P2X₃ receptor expression of L4/L5 DRG and spinal cord in group V was higher than those in groups I–III (p < 0.01) or group IV (p < 0.05). The mechanical withdrawal threshold, thermal withdrawal latency and P2X₃ immunoreactivity of L4/L5 DRG and spinal cord in group IV showed no significant difference compared with those in groups I, II or III (p > 0.05). The amplitudes of the currents in group V (CCI) were much larger than those obtained in other groups after application of same concentration adenosine 5′-triphosphate disodium (ATP) (p < 0.01). α,β-Methylene-ATP (α,β-meATP)-activated currents in DRG neurons of CCI rats were more obvious than those obtained in other group rats (p < 0.01). The results showed that TMP may inhibit the primary afferent transmission of neuropathic pain induced by P2X₃ receptor.     

Effect of puerarin on P2X3 receptor involved in hyperalgesia after burn injury in the rat

The study investigated the effects of puerarin on P2X₃ receptor involved in hyperalgesia after burn injury in the rat. Superficial second degree burn injury models were adopted. Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured and the P2X₃ receptor expressions in dorsal root ganglion (DRG) from burn injury models rats were detected by immunohistochemistry, in situ hybridization, RT-PCR and western blot. MWL and TWL in untreated superficial second paw burn rats were reduced. MWL and TWL of puerarin-treated superficial second paw burn rats showed significant increase compared with untreated superficial second paw burn rats. Puerarin can decrease the hyperalgesia after burn injury. At day 3 post-burn, the expressions of P2X₃ protein and mRNA in DRG neurons in untreated superficial second degree back burn group were increased significantly compared with sham back burn group, puerarin-treated back unburned control group, blank back control group, while in puerarin-treated superficial second degree back burn group, the P2X₃ protein and mRNA expressions were decreased markedly. There is no significant difference in sham back burn group, puerarin-treated back unburned control group, blank back control group. Therefore, puerarin may reduce the nociceptive transmission of burn injury pain mediated by P2X₃ receptor and alleviate P2X₃ receptor involved in hyperalgesia after burn injury in the rats.     

Role of puerarin in the signalling of neuropathic pain mediated by P2X3 receptor of dorsal root ganglion neurons

Tissue injury or inflammation of the nervous system may result in chronic neuropathic pain characterized by sensitivity to painful stimuli. P2X₃ receptors play a crucial role in facilitating pain transmission. Puerarin is an active compound of a traditional Chinese medicine Ge-gen, and Ge-gen soup has anti-inflammatory effects. The present research investigated the role of puerarin in the signalling of chronic neuropathic pain mediated by P2X₃ receptors of rat dorsal root ganglion neurons. Chronic constriction injury (CCI) rat model was adopted. Sprague-Dawley rats were randomly divided into blank control group (Ctrl), sham group (Sham), puerarin-treated control group (Ctrl + PUE), chronic constriction injury (CCI) group and puerarin-treated CCI group (CCI + PUE). Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured by the von-Frey test and the Hargreaves’ test respectively. The stain values of P2X₃ protein and mRNA in L4/L5 dorsal root ganglion (DRG) were detected by immunohistochemistry, western blot and in situ hybridization. At day 4-7 after the operation of CCI rats, MWT and TWL in group CCI and CCI + PUE were lower than those in group Ctrl, Sham and Ctrl + PUE, while there was no difference among group Ctrl, Sham and Ctrl + PUE. At day 7-10 after operation, MWT and TWL in group CCI + PUE was higher than those in group CCI, but there was no significant difference between group CCI + PUE and group Ctrl (p > 0.05). At day 14 after operation, the stain values of P2X₃ proteins and mRNAs in L4/L5 DRG of group CCI were higher than those in group Ctrl, Sham, Ctrl + PUE and CCI + PUE, while the stain values of P2X₃ proteins and mRNAs in group CCI + PUE were significantly decreased compared with those in group CCI. Therefore, puerarin may alleviate neuropathic pain mediated by P2X₃ receptors in dorsal root ganglion neurons.     

Spinal P2X(7) receptor mediates microglia activation-induced neuropathic pain in the sciatic nerve injury rat model

P2X₇ receptor is an important member of ATP-sensitive ionotropic P2X receptors family, which includes seven receptor subtypes (P2X₁-P2X₇). Recent evidence indicates that P2X₇R participates in the onset and persistence of neuropathic pain. In tetanic stimulation of the sciatic nerve model, P2X₇R was involved in the activation of microglia, but whether this happens in other neuropathic pain models remains unclear. In this study we used immunohistochemistry and Western blot to explore the relationship of P2X₇R expression with microglia activation, and with mechanical allodynia and thermal hypersensitivity in the chronic constriction of the sciatic nerve (CCI) rat model. The results show that following nerve ligature, mechanical allodynia and thermal hypersensitivity were developed within 3 days (d), peaked at 14 d and persisted for 21 d on the injured side. P2X₇R levels in the ipsilateral L4-6 spinal cord were increased markedly after injury and the highest levels were observed on day 14, significant difference was observed at I-IV layers of the dorsal horn. The change in P2X₇R levels in the spinal cord was consistent with the development of mechanical allodynia and thermal hypersensitivity. Intrathecal administration of the P2X₇R antagonist Brilliant Blue G (BBG) reversed CCI-induced mechanical allodynia and thermal hypersensitivity. Double-labeled immunofluorescence showed that P2X₇R expression were restricted to microglia, spinal microglia were activated after nerve injury, which was inhibited by BBG. These results indicated that spinal P2X₇R mediate microglia activation, this process may play an important role in development of mechanical allodynia and thermal hypersensitivity in CCI model.     

P2X7 receptors in cerebral ischemia

Cerebral ischemia is one of the most common diseases resulting in death and disability in aged people. It leads immediately to rapid energy failure, ATP depletion, and ionic imbalance, which increase extracellular ATP levels and accordingly activate P2X₇ receptors. These receptors are ATP-gated cation channels and widely distributed in nerve cells, especially in the immunocompetent cells of the brain. Currently, interest in the roles of P2X₇ receptors in ischemic brain injury is growing. In this review, we discuss recent research progress on the actions of P2X₇ receptors, their possible mechanisms in cerebral ischemia, and the potential therapeutic value of P2X₇ receptor antagonists which may provide a new target both for clinical and for research purposes.     

The First CNS-Active Carborane: A Novel P2X7 Receptor Antagonist with Antidepressant Activity

相似文献   

Electroacupuncture regulates glucose-inhibited neurons in treatment of simple obesity

The glucose-inhibited neurons present in the lateral hypothalamic area are regarded as glucose detectors. This structure is involved in the regulation of food intake through extracellular blood glucose concentrations, and plays a crucial role in obesity onset. In the present study, obesity models established with high fat feeding were treated with electroacupuncture at Zusanli (ST36)/ Inner Court (ST44) on the left side and Tianshu (ST25) bilaterally. We found that electroacupuncture could effectively reduce body weight and the fat-weight ratio, and decrease serum leptin, resistin, tumor necrosis factor alpha, and neuropeptide Y levels, while increase serum adiponectin and cholecystokinin-8 levels. This treatment altered the electrical activity of glucose-inhibited neurons in the lateral hypothalamic area, with electroacupuncture at Zusanli/ Inner Court exerting an inhibitory effect, while electroacupuncture at bilateral Tianshu exerting an excitatory effect. These data suggest that electroacupuncture at the lower limbs and abdominal cavity is an effective means for regulating the activity of glucose-inhibited neurons in the lateral hypothalamic area and for improving the secretory function of adipose tissue.     

Microencapsulation improves inhibitory effects of transplanted olfactory ensheathing cells on pain after sciatic nerve injury

Olfactory bulb tissue transplantation inhibits P2X2/3 receptor-mediated neuropathic pain. However, the olfactory bulb has a complex cellular composition, and the mechanism underlying the action of purified transplanted olfactory ensheathing cells(OECs) remains unclear. In the present study, we microencapsulated OECs in alginic acid, and transplanted free and microencapsulated OECs into the region surrounding the injured sciatic nerve in rat models of chronic constriction injury. We assessed mechanical nociception in the rat models 7 and 14 days after surgery by measuring paw withdrawal threshold, and examined P2X2/3 receptor expression in L4–5 dorsal root ganglia using immunohistochemistry. Rats that received free and microencapsulated OEC transplants showed greater withdrawal thresholds than untreated model rats, and weaker P2X2/3 receptor immunoreactivity in dorsal root ganglia. At 14 days, paw withdrawal threshold was much higher in the microencapsulated OEC-treated animals. Our results confirm that microencapsulated OEC transplantation suppresses P2X2/3 receptor expression in L4–5 dorsal root ganglia in rat models of neuropathic pain and reduces allodynia, and also suggest that transplantation of microencapsulated OECs is more effective than transplantation of free OECs for the treatment of neuropathic pain.     

Electroacupuncture and A‐317491 depress the transmission of pain on primary afferent mediated by the P2X3 receptor in rats with chronic neuropathic pain states

P2X is a family of ligand‐gated ion channels that act through adenosine ATP. The P2X₃ receptor plays a key role in the transmission of neuropathic pain at peripheral and spinal sites. Electroacupuncture (EA) has been used to treat neuropathic pain effectively. To determine the role of EA in neuropathic pain mediated through the P2X₃ receptor in dorsal root ganglion neurons and the spinal cord, a chronic constriction injury (CCI) model was used. Sprague‐Dawley rats were divided into four groups: sham CCI, CCI, CCI plus contralateral EA, and CCI plus ipsilateral EA. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were recorded. Furthermore, the expression of the P2X₃ receptor was evaluated through Western blotting and immunofluorescence. The effects of EA and A‐317491 were investigated through the whole‐cell patch‐clamp method and intrathecal administration. Our results show that the MWT and TWL of EA groups were higher than those in the CCI group, whereas the expression of the P2X₃ receptor was lower than that in the CCI group. However, no significant difference was detected between the two EA groups. EA depressed the currents created by ATP and the upregulation of the P2X₃ receptor in CCI rats. Additionally, EA was more potent in reducing mechanical allodynia and thermal hyperalgesia when combined with A‐317491 through intrathecal administration. These results show that both contralateral and ipsilateral EA might inhibit the primary afferent transmission of neuropathic pain induced through the P2X₃ receptor. In addition, EA and A‐317491 might have an additive effect in inhibiting the transmission of pain mediated by the P2X₃ receptor. © 2014 Wiley Periodicals, Inc.     

Overexpression of GRK6 alleviates chronic visceral hypersensitivity through downregulation of P2Y6 receptors in anterior cingulate cortex of rats with prenatal maternal stress

AimsVisceral hypersensitivity is a major clinic symptom in patients with irritable bowel syndrome (IBS). Anterior cingulate cortex (ACC) is involved in processing the information of pain. Both G protein‐coupled receptor kinase 6 (GRK6) and P2Y purinoceptor 6 (P2Y6) are associated with neuroinflammation and pathological pain. The aim of this study was to investigate the interaction between GRK6 and P2Y6 in ACC in the development of visceral hypersensitivity of adult offspring rats with prenatal maternal stress (PMS).MethodsVisceral hypersensitivity was quantified by abdominal withdrawal reflex threshold to colorectal distension (CRD). The expression and cellular distribution of GRK6 and P2Y6 were determined by Western blotting, qPCR, and fluorescence immunohistochemistry. Co‐immunoprecipitation was used to evaluate the interaction between GRK6 and P2Y6.ResultsThe mRNA and protein levels of GRK6 were significantly decreased in ACC of PMS rats. The injection of GRK6 overexpression virus significantly attenuated visceral hypersensitivity of PMS rats. P2Y6’s mRNA level, protein level, and ratio of membrane protein over total protein expression was markedly increased in PMS rats. P2Y6 antagonist MRS2578 microinjection reversed visceral hypersensitivity of PMS rats. GRK6 overexpression significantly reduced P2Y6’s expression in membrane proteins and P2Y6’s ratio of membrane protein over total protein expression.ConclusionsThese results indicate that decreased GRK6 leads to the accumulation of P2Y6 at neuron membrane in ACC, thereby contributing to visceral hypersensitivity of PMS rats.     

P2X7 inhibition in stellate ganglia prevents the increased sympathoexcitatory reflex via sensory-sympathetic coupling induced by myocardial ischemic injury

Purinergic signaling has been found to participate in the regulation of cardiovascular function. In this study, using a rat myocardial ischemic injury model, the sympathoexcitatory reflex mediated by P2X₇ receptor via sensory-sympathetic coupling between cervical dorsal root ganglia (DRG) nerves and stellate ganglia (SG) nerves was explored. Our results showed that the systolic blood pressure, heart rate, serum cardiac enzymes concentrations, interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) concentrations were increased, and the expression levels of P2X₇ mRNA and protein in DRG and SG were up-regulated after myocardial ischemic injury. Administration of brilliant blue G (BBG), a selective P2X₇ antagonist, decreased the elevation of systolic blood pressure, heart rate, serum cardiac enzyme, IL-6 and TNF-α, and inhibited the up-regulated expression of P2X₇ mRNA and protein in DRG and SG after myocardial ischemic injury. Retrograde tracing test showed that there were calcitonin gene-related peptide sensory nerves and substance P sensory nerves sprouting from DRG to SG, which played an important role in the development of myocardial ischemic injury. The up-regulated P2X₇ receptor expression levels on the surface membrane of satellite glial cells contributed to the activation of sensory-sympathetic coupling, which in turn facilitated the sympathoexcitatory reflex. BBG can inhibit the activation of satellite glial cells and interrupt the generation of sensory-sympathetic coupling in the cervical sympathetic ganglia after the myocardial ischemic injury. Taken together, these findings may provide a new therapeutic approach for treating coronary heart disease, hypertension and other cardiovascular diseases.     

Transient changes in P2X3 but not TRPV1 mRNA expression in rat after prenatal exposure to glucocorticoids

TRPV(1) and P2X(3) receptors are cation channels known to modulate responses to noxious stimuli. In the nervous system, these receptors are preferentially expressed in the pathways that transmit pain signal from the periphery to the brain. The aim of this study is to determine whether prenatal exposure to glucocorticoids alters the expression of P2X(3) and TRPV(1) in the dorsal root ganglia (DRG) and spinal cord (SC) during early postnatal development. Time-pregnant rats received daily subcutaneous injection of dexamethasone (100 microg/kg/day) or a vehicle from prenatal days 9 to 20. The DRG and lumbar/sacral SC of the newborn rats were harvested on postnatal days 1, 7, and 42 for a quantitative real-time PCR analysis of messenger RNAs. In the control rats, mRNA level of P2X(3) and TRPV(1) receptors from DRG remained relatively constant from postnatal days 1 to 42 while those from SC were significantly higher on postnatal day 42 than days 1 and 7. Prenatal treatment with dexamethasone significantly decreased P2X(3) receptor mRNA level in the DRG and SC on postnatal day 1. Such an effect was no longer statistically significant on postnatal day 7, and disappeared completely on postnatal day 42. Expression of TRPV 1 was not altered by dexamethasone regardless of anatomical localization or developmental stages. Therefore, prenatal exposure to glucocorticoids leads to a transient inhibition of P2X(3) expression in the DRG and SC, suggesting a potential involvement of P2X(3) receptors in the unique profile of pain perception in neonates.     

慢性内脏高敏感性大鼠电针后脊髓和大脑c-Fos的表达

BACKGROUND： Visceral hypersensitivity is the main cause of irritable bowel syndrome, c-Fos is a marker of visceral hypersensitivity in the central nervous system. Electroacupuncture can relieve chronic visceral hypersensitivity in rats, but the mechanism is still unknown. OBJECTIVE： To identify c-Fos expression in the spinal cord and cerebral cortex of rats with chronic visceral hypersensitivity, and to test the effects of electroacupuncture on pain sensitivity in rats with chronic visceral hypersensitivity. DESIGN, TIME AND SETTING： A randomized controlled animal experiment was performed at the Animal E：~perimental Center, Shanghai University of Traditional Chinese Medicine, from January to April, 2007. MATERIALS： A total of 24 neonatal, male, Sprague Dawley rats, aged five days old, were equally and randomly assigned into a normal group, a model group, and an electroacupuncture group. Rabbit anti-rat c-Fos antibody and Evision secondary antibody kits （Sigma, USA）, diaminobenzidine kit （Dako, Denmark）, and an LD202H electroacupuncture apparatus （Huawei, Beijing, China） were used in this study. METHODS： Neonatal rats from the model and electroacupuncture groups were used to establish rat models of chronic visceral hypersensitivity by the saccule stimulation method. After model establishment, 0.25 mm diameter electric needles were inserted into Tianshu （ST 25） and Shangjuxu （ST37） at a depth of approximately 0.5 cm, with an square wave （alternating current frequency at 100/20 Hz, amplitude ranged 0.2-0.6 ms, intensity at 1 mA） once for 20 minutes, once a day, for seven days. Rats in the normal and model groups were not treated. MAIN OUTCOME MEASURES： Following 7 days of treatment, c-Fos expression in the spinal cord and cerebral cortex was detected by immunohistochemistry. After the first electroacupuncture treatment, abdominal withdrawal reflex scores were investigated to evaluate the pain threshold for chronic visceral hypersensitivity in rats. RESULTS： Visceral hypersensitivity increased c-Fos staining （P 〈 0.05）, and electroacupuncture significantly decreased the number of these cells to near normal levels （P 〉 0.05）. Abdominal withdrawal reflex scores were significantly lower in the electroacupuncture and normal groups than in the model group （P 〈 0.05） and were similar between the electroacupuncture and normal groups （P 〉 0.05）. CONCLUSION： Electroacupuncture decreases c-Fos expression in the spinal cord and cerebral cortex and increases pain threshold in a chronic visceral hypersensitivity model in rats.     

Expressions of P2X2 and P2X3 receptors in rat nodose neurons after myocardial ischemia injury

The role of ATP is as a functional neurotransmitter and local intercellular signaling molecule. The nodose neurons express both P2X₂ and P2X₃ subunits in their plasma membrane. This study wants to observe the expression of P2X₂ receptor and the expression relationship between P2X₂ and P2X₃ in nodose neurons after myocardial ischemic injury. The expressions of P2X₃ immunoreactivity, mRNA and protein were analyzed by immunohistochemistry, in situ hybridization and western blotting. P2X₂ and P2X₃ immunoreactivity, mRNA expression had been increased after myocardial ischemia in nodose neurons. Myocardial ischemia enhanced P2X₂ and P2X₃ protein level in nodose ganglia after myocardial ischemia. P2X₂ receptor in nodose neurons participated in the transmission of cardiac pain. The changes of P2X₂ and P2X₃ immunoreactivities, mRNA and protein that occurred following myocardial ischemic injury in the nodose ganglia showed that a correlation existed between P2X₂ and P2X₃ expression. It suggests that P2X₂ receptor subtype in company with P2X₃ receptor subtype plays the important role in cardiac vagal sensory nociceptors with a sensitivity to ATP.     

P2X3 is expressed by DRG neurons that terminate in inner lamina II

The P2X₃ receptor subunit, a member of the P2X family of ATP-gated ion channels, is almost exclusively localized in sensory neurons. In the present study, we sought to gain insight into the role of P2X₃ and P2X₃-containing neurons in sensory transmission, using immunohistochemical approaches. In rat dorsal root ganglia (DRG), P2X₃-immunoreactivity (-ir) was observed in small- and medium-sized neurons. Approximately 40% of DRG neuronal profiles in normal rats contained P2X₃-ir. In rats that had received neonatal capsaicin treatment, the number of P2X₃-positive neurons was decreased by approximately 70%. Analysis of the colocalization of P2X₃-ir with cytochemical markers of DRG neurons indicated that approximately 94% of the P2X₃-positive neuronal profiles were labelled by isolectin B₄ from Bandeiraea simplicifolia, while only 3% contained substance P-ir, and 7% contained somatostatin-ir. In dorsal horn of rat spinal cord, P2X₃-ir was observed in the inner portion of lamina II and was reduced subsequent to dorsal rhizotomy, as well as subsequent to neonatal capsaicin treatment. Finally, P2X₃-ir accumulated proximal to the site of sciatic nerve ligation, and was seen in nerve fibres in skin and corneal epithelium. In summary, our results suggest that P2X₃ is expressed by a functionally heterogeneous population of BSI-B₄-binding sensory neurons, and is transported into both central and peripheral processes of these neurons.     

Single nucleotide polymorphisms that were identified in affective mood disorders affect ATP-activated P2X7 receptor functions

Genetic linkage studies have previously identified many single non-synonymous nucleotide polymorphisms (SNPs) in the human P2RX7 gene in individuals with affective mood disorders. The P2RX7 gene encodes the P2X₇ receptor (P2X₇R) that operates as an ATP-activated Ca²⁺-permeable cationic channel and induces formation of a large pore, the two functional properties that are critical for the physiological and pathological roles of the receptor. The current knowledge regarding the effects of SNPs on the P2X₇R functional properties, which is indispensable to help elucidate the disease mechanism, is limited. In this study, we introduced by site-directed mutagenesis twelve SNP mutations in the human P2X₇ receptor that were previously identified in or associated with affective mood disorders, expressed the resultant mutants in human embryonic kidney cells, and characterized their functional properties by electrophysiology. All mutations except Q460R gave rise to profound effects on the P2X₇R function. G150R, E186K and I568N conferred complete loss of function. V76A, R117W, L191P, T357S and E496A resulted in strong impairment of, whereas H155Y and A348T caused significant increase in, both ATP-activated ion channel function and pore formation. Q521H reduced the receptor’s sensitivity to extracellular Ca²⁺ inhibition. An atomic structure model of the human P2X₇R, based on the crystal structure of the zebrafish P2X₄ receptor, suggests that the SNP mutational effects may result from changes in subunit interaction, agonist binding and/or channel gating. These results provide essential knowledge for a better understanding of the relationships between human P2RX7 SNPs and associated pathologies as well as the receptor structure-function relationships.