The Inhibition by Guanfu Base A of Neuropathic Pain Mediated by P2Y12 Receptor in Dorsal Root Ganglia.

Activation of satellite glial cells (SGCs) in the dorsal root ganglia (DRG) is involved in mechanical and thermal hyperalgesia. The upregulated P2Y12 receptor expressed in SGCs of the DRG participates in the nociceptive transmission of neuropathic pain. Guanfu base A (GFA) has been reported to exhibit antiarrhythmic and anti-inflammatory effects. In this study, we explored the effects of GFA on P2Y12 receptor-mediated mechanical and thermal hyperalgesia in chronic constriction injury (CCI) rats. Sprague-Dawley rats were randomly divided into sham operation group (Sham), CCI operation group (CCI), CCI rats treated with guanfu base A group (CCI + GFA) and control rats treated with GFA group (Ctrl + GFA). Mechanical withdrawal threshold and thermal withdrawal latency were measured. P2Y12 expression in L4-L6 dorsal root ganglion (DRG) was detected by quantitative real-time PCR and Western blot. After CCI treatment, mechanical and thermal hyperalgesia and the expression values of P2Y12 receptor mRNA and protein in DRG were increased. Dual-labeling immunofluorescence showed that the coexpression of P2Y12 receptor and glial fibrillary acidic protein (GFAP) in the DRG of CCI rats was increased compared to sham rats. GFA relieved mechanical and thermal hyperalgesia in the CCI rats, decreased the expression of P2Y12 mRNA and protein and phosphorylation of p38 MAPK in the DRG, and increased the ADP-downregulated cAMP concentrations in HEK293 cells transfected with P2Y12 plasmid. After CCI rats were treated with GFA, the coexpression of P2Y12 receptor and GFAP in the DRG was significantly decreased compared to the untreated CCI group. Thus, downregulating the P2Y12 receptor relieved mechanical and thermal hyperalgesia in the CCI rats.

Increased sympathoexcitatory reflex induced by myocardial ischemic nociceptive signaling via P2X2/3 receptor in rat superior cervical ganglia.

The restructuring of cardiac innervation after myocardial ischemic injury, which is often associated with an increased sympathoexcitatory reflex characterized by an increase in blood pressure and sympathetic nerve activity. This study observed whether P2X(2/3) receptor in rat superior cervical ganglion (SCG) played a role in the increased sympathoexcitatory reflex induced by myocardial ischemic nociceptive signaling. The findings showed that the systolic blood pressure, heart rate and respiration in the myocardial ischemic rats were higher than those in control rats. The content of adenosine 5'-triphosphate (ATP) from myocardial ischemic group was higher than that from control group. After myocardial ischemic rats were treated with selective P2X(2/3) receptor antagonist A-317491, the content of ATP in SCG was reduced. Coexpression value of P2X(2), P2X(3) and tyrosine hydroxylase (TH) in the SCG and myocardial tissues of myocardial ischemic group was increased significantly, compared with that in the SCG and myocardial tissues of control group. The expression value of P2X(2), P2X(3) and TH in the SCG and myocardial tissues of myocardial ischemic rats treated with A-317491 was decreased. The amplitude of the currents was much larger in myocardial ischemic group than that obtained in control group after administration of ATP with the same concentration. After the myocardial ischemic rats were treated with A-317491, ATP-activated currents were reduced. The myocardial ischemic injury induced an increase in the expression of P2X(2/3) receptor colocalization with TH and a hypersensitivity state of SCG neurons to ATP, which led to the increased sympathoexcitatory reflex.

Effect of tetramethylpyrazine on DRG neuron P2X3 receptor involved in transmitting pain after burn.

UNLABELLED: A burn is a severe injury, and the resulting pain can be very significant. Currently, opioids are the primary method of pain management, but these drugs have side effects; thus, it is of prime focus to research the mechanisms of pain formation and analgesic drugs. OBJECTIVE: To investigate the effects of tetramethylpyrazine (TMP) on burn pain mediated by the P2X3 receptor. METHODS: First-degree and superficial second-degree burn models were used. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured, and P2X3 receptor expression on nerve terminals in burn-injured skin were detected by immunohistochemistry. The effects of TMP on the P2X receptor agonist-activated currents in freshly isolated burn-injured rat dorsal root ganglion (DRG) neurons were studied by whole-cell patch-clamp technique. MAIN RESULTS: One hour following the procedure, MWT and TWL in first and second-degree paw-burns with normal saline (NS) treatment were lower than those in the unburned control group and lasted for 24 or 96 h, respectively (p<0.01). After 24 h, MWT and TWL in the first-degree paw-burn with TMP treatment were significantly increased as compared with NS treatment; no difference was found when compared to the unburned control group. MWT and TWL in the second-degree paw-burn in the TMP treatment group were significantly increased at 48 h compared to NS treatment. No difference was found with the values for the unburned control group after 72 h. On day 3 after the burn, P2X3-receptor expression in the nerve terminal in the burn-injured skin of the first- and second-degree dorsal burns in the NS treatment group was higher than those in other groups (p<0.05). After treatment with TMP, P2X3-receptor expression of the nerve terminal in the first- and second-degree dorsal burns of the TMP treatment group was significantly decreased. ATP-activated currents (IATP) on the DRG neurons of the second-degree dorsal burn in the NS treatment group were markedly higher than those in the second-degree dorsal burns in the TMP treatment group and the unburned control group (p<0.05); there were no significant differences between the second-degree dorsal burn in the TMP treatment group and the unburned control group (p>0.05). CONCLUSION: TMP alleviates nociceptive transmission of burn-injury pain mediated by the P2X3 receptor.

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 P2X(2) and P2X(3) subunits in their plasma membrane. This study wants to observe the expression of P2X(2) receptor and the expression relationship between P2X(2) and P2X(3) in nodose neurons after myocardial ischemic injury. The expressions of P2X(3) immunoreactivity, mRNA and protein were analyzed by immunohistochemistry, in situ hybridization and western blotting. P2X(2) and P2X(3) immunoreactivity, mRNA expression had been increased after myocardial ischemia in nodose neurons. Myocardial ischemia enhanced P2X(2) and P2X(3) protein level in nodose ganglia after myocardial ischemia. P2X(2) receptor in nodose neurons participated in the transmission of cardiac pain. The changes of P2X(2) and P2X(3) immunoreactivities, mRNA and protein that occurred following myocardial ischemic injury in the nodose ganglia showed that a correlation existed between P2X(2) and P2X(3) expression. It suggests that P2X(2) receptor subtype in company with P2X(3) receptor subtype plays the important role in cardiac vagal sensory nociceptors with a sensitivity to ATP.

[Quantification of pentoxyverine citrate in human plasma by LC-ESI/MS method and its application].

A rapid and sensitive liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI/ MS) method for quantification of pentoxyverine citrate in human plasma has been developed and applied for the bioequivalence and pharmacokinetics study. After extracted from plasma samples with ethyl acetate, analysis was performed in selected ion monitoring (SIM) mode with a positive electrospray ionization (ESI) interface with a mobile phase consisted of methanol and water (0.4% glacial acetic acid and 4 mmol x L(-1) ammonium acetate, 43 : 57, v/v). The linear concentration range of the calibration curves was 1.0-160.0 ng x mL(-1) for pentoxyverine citrate, inter- and intra-precision (RSD) was less than 12.5%, accuracy (RE) was in +/- 13.5% and absolute recovery was more than 80%. The method was proved simple, rapid, sensitive, specific and suitable for pharmacokinetic and bioequivalence study of Yufenweilin capsule containing pentoxyverine citrate.