Analgesic Effect Of Oxysophoridine With Intrathecal Injection And Its Influence On Central GABAA Receptor

Objective: To study the analgesic effect of oxysophoridine(OSR) with intrathecal injection(ith), analyze the interaction between OSR andγ-aminobutyric acid A receptor(GABAA receptor)agonist or GABAA receptor antagonist, inspect its influence on the mRNA and protein expression of GABA_ARα1 ,and then analyze molecule mechanism of OSR.Methods: 1. Behavioral pharmacology:①The Warm water tail-flick test were used to observe the analgesic effect with ith and Intra peritoneoinjection(ip)injection;②GABAA receptor agonists or antagonists were used to study its influence on the analgesic effect of OSR and analyze the related mechanism;2. Quantitative Real-Time PCR: The Quantitative Real-Time PCR method was used to inspect the influence of OSR on GABA_ARα1mRNA expression of spinal cord and brain in mice, then analyze the influence of OSR on mRNA expression of GABA_ARα1;3. Western blot: The Western blot method was used to inspect the influence of OSR on the protein expression of GABA_ARα1 of spinal cord and brain in the formalin test in mice, then analyze the influence of the analgesic effect of OSR on the protein expression of GABA_ARα1 receptor;4. Immunohistochemistry(SABC)The Immunohistochemistry method was used to detect the influence of OSR on the immune positive cell number of GABA_ARα1 in spinal cord to study the influence of the analgesic effect of OSR on the immune positive number of GABA_ARα1.Results: 1. Analgesic effect of ith OSR: OSR(12.5, 6.25 mg/kg, ith)can significantly allays pain in the warm water tail-flick test at 10, 20, 30, 45, 60, 90 min post-dose(P<0.05, P<0.01) . The maximum rate of pain threshold can be up to 68.45 % at 20 min post-dose;2. The influence of GABAA receptor agonist or GABAA receptor antagonist on the analgesic effect of OSR: GABA (1.6 mg/kg, icv) and muscimol(MUS, 0.1μg/mouse, icv) can remarkably strengthen the analgesic effect of OSR (3.13 mg/kg, ith) in the warm water tail-flick test(P<0.05, P<0.01), picrotoxin ( PIC, 2 mg/kg, ip) and bicuculine(BIC, 0.2μg/mouse, ith) can significantly antagonize against the analgesic effect of OSR (6.25 mg/kg, ith) in the warm water tail-flick test(P<0.05, P<0.01). The results indicate that GABAA receptor is involved in the analgesic effect of OSR;3. The influence of OSR on the immune positive cell number of GABA_ARα1 in spinal cord: OSR (12.5 mg/kg, ith) can significantly increase the positive cell number of GABA_ARα1 in spinal cord (P<0.01) and siginificantly decrease the mean gray lever(P<0.01). The result indicates that the analgesic effect of OSR has some relation with the expression of positive cell number of GABA_ARα1 in spinal cord;4. The influence of OSR on the GABA_ARα1 mRNA and protein expression in the spinal and brain in the formalin test: OSR(12.5 mg/kg, ith)can significantly increase GABA_ARα1 mRNA and protein expression in spinal cord and brain(P<0.01); OSR(500 mg/kg, iv)presents the same result. The result indicates that the expression of GABA_ARα1 mRNA and protein is involved in the mechanism.Conclusion: OSR has significant analgesic effect; GABAA receptor is involved in the analgesic mechanism. The mechanism has some relation with the up-regulation of GABA_ARα1 in spinal cord.