Intensity in the thermal stimulus was adjusted to attain an typical baseline paw-withdrawal latency of

Intensity in the thermal stimulus was adjusted to attain an typical baseline paw-withdrawal latency of approximately 9 to 12 seconds in naive mice. Only speedy hind-paw movements (with or without the need of licking from the hind paws) away in the stimulus have been regarded as to be a withdrawal response. Paw movements linked with locomotion or weight-shifting were not counted as a response. The paws had been measured alternating among the left and right with an interval of much more than 3 NOP Receptor/ORL1 Agonist drug minutes between measurements. The latency of paw withdrawal right after the thermal stimulus was determined as the average of 3 measurements per paw. Statistical analysis The information from the [35S]GTPS binding assay are expressed because the mean ?typical error in the mean (SEM) of Stimulation. The data concerning hyperalgesic responses are shown as the imply ?SEM of your paw-withdrawal latency. Receptor binding curves were fitted utilizing Graph-Pad Prism 4.0 (Graph-Pad Computer software Inc., La Jolla, CA, USA). The statistical significance of variations involving groups was assessed by two-way analysis of variance followed by the Bonferroni/Dunn several comparison test or Student’s t-test.NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author ManuscriptRESULTSEffect of single or repeated subcutaneous (s.c.) injections of morphine, fentanyl or oxycodone on the neuropathic pain-like state induced by nerve injury in mice In the present study, mice with partial sciatic nerve P2X1 Receptor Antagonist Gene ID ligation exhibited marked neuropathic pain-like behavior only for the ipsilateral side at 7 days soon after nerve ligation (P 0.001 versus sham-saline group, Fig. 1). The persistent painful state attributable to sciatic nerve ligation lasted for far more than 21 days after surgery in mice (Fig. 2). A single s.c. injection of either morphine (1?0 mg/kg), fentanyl (0.003?.01 mg/kg) or oxycodone (0.1? mg/kg) at 7 days after sciatic nerve ligation recovered the decreased thermal threshold observed on the ipsilateral side in sciatic nerve-ligated mice in a dose-dependent manner, and maximal antihyperalgesic responses have been observed at 30, 15 or 15 minutes after the injection of morphine, fentanyl or oxycodone, respectively (P 0.05, P 0.01 or P 0.001 versus shamsaline group, Fig. 1). At a dose of 5.0 mg/kg, 0.03 mg/kg or 0.five mg/kg, s.c. administration of morphine, fentanyl or oxycodone pretty much totally reversed the decrease in the thermal threshold without the need of excessive effects in sciatic nerve-ligated mice.As a result, we proposed that the optimal doses for the morphine-, fentanyl- or oxycodone-induced antihyperalgesiceffectinnerve-ligatedmicewere5.0,0.03or0.five mg/kg, respectively. As shown in Fig. 2a and c, the thermal hyperalgesia observed around the ipsilateral side soon after nerve ligation was clearly reversed by each repeated s.c. injection of morphine (five mg/kg) or oxycodone (0.5 mg/kg) once a day for 14 consecutive days from 7 days following nerve ligation. In contrast, the antihyperalgesic effect following repeated treatment with fentanyl (0.03 mg/kg) was gradually tolerated (P 0.01 or P 0.001 versus sham-saline group; Fig. 2b).Addict Biol. Author manuscript; out there in PMC 2014 January 01.Narita et al.PageChanges in G-protein activation induced by repeated subcutaneous (s.c.) injection of morphine, fentanyl or oxycodone inside the spinal cord of mice with nerve ligation We investigated the capability of morphine, fentanyl or oxycodone to activate G-proteins by means of the stimulation of MOR in membranes with the ipsilateral side in the spinal cord obta.