Effects of intrathecal and i.c.v. administration of neuropeptide W-23 and neuropeptide B on the mechanical allodynia induced by partial sciatic nerve ligation in rats

Neuropeptide W-23 and neuropeptide B are each an endogenous ligand of GPR7. GPR7 mRNA has been detected in regions of the cortex, the hippocampus, the hypothalamus and the spinal cord in the rat. GPR7 receptor has structural features in common with both opioid and somatostatin receptors. In the present study, the effects of intrathecal and i.c.v. application of neuropeptide W-23 and neuropeptide B on the level of mechanical allodynia induced by partial sciatic nerve ligation were tested in rats. The level of mechanical allodynia was measured using von Frey filaments. Intrathecal injection of either neuropeptide W-23 or neuropeptide B attenuated the level of mechanical allodynia in a dose dependent manner at a dose between 0.1 and 10 microg, but i.c.v. injection of either neuropeptide W-23 or neuropeptide B had no effect on the level of mechanical allodynia at a dose between 3 and 30 microg. The effect of intrathecal administration of either 10 microg of neuropeptide W-23 or 10 microg of neuropeptide B was not antagonized by i.p. injection of 1 mg/kg of naloxone. Immunohistochemical examination revealed that neuropeptide W-23 was expressed mainly in the small- to medium-sized neuronal profiles in the dorsal root ganglion and that partial sciatic nerve injury decreased the percentage of neuropeptide W-23-like immunoreactivity positive neuronal profiles that were labeled by IB4. These data suggest that neuropeptide W-23 is involved in the nociceptive transmission in spinal cord and that both spinally-applied neuropeptide W-23 and spinally-applied neuropeptide B produce anti-allodynic effects in the partial sciatic nerve ligation model in rat.     

The role of ultrasound-guided single-shot femoral and sciatic nerve blocks on pain management after total knee arthroplasty

BackgroundPeripheral nerve blocks reduce postoperative pain and opioid consumption after total knee arthroplasty (TKA). The aim of this study was to evaluate the effects of single-shot femoral nerve and sciatic nerve blocks on postoperative pain management and opioid consumption after TKA.MethodsThis study included 100 patients who underwent TKA between July 2015 and September 2017. Fifty patients received pre-operative, single-injection, ultrasound-guided femoral and sciatic nerve blocks (Group 1) and 50 did not (Group 2). Multimodal analgesia was otherwise identical, and oxycodone was administered either intravenously or orally if the patients complained of postoperative pain ≥ 6 on the visual analog scale (VAS). Postoperative VAS scores, opioid consumption, and the fear of future TKA were compared between the groups.ResultsThe mean VAS in the first 18 postoperative hours was significantly lower in Group 1 (P ≤ 0.002). The mean amount of oxycodone taken in the first three postoperative days was significantly lower in Group 1 (P = 0.001). Patient fear of future TKA at 14 days postoperatively was significantly lower in Group 1 (P = 0.027).ConclusionsPre-operative ultrasound-guided, single-shot femoral and sciatic nerve blocks afforded effective pain control in the first 18 h after TKA, and significantly reduced oxycodone consumption in the first three postoperative days.