Effects of dezocine on diabetic neuropathic pain and expression of NMDA receptor subunit 2B in spinal dorsal horns of rats / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the effects of dezocine on diabetic neuropathic pain (DNP ) and expression of NMDA receptor subunit 2B (NR2B) in the spinal dorsal horns of rats .Methods Forty-eight male Sprague-Dawley rats , aged 4 weeks , weighing 150-170 g , with DNP induced by intraperitoneal injection of streptozocin (STZ) 50 mg/kg (successful induction of diabetes was defined as blood glucose >16.7 mmol/L) , were randomly divided into 2 groups ( n=24 each) using a random number tableDNP group and dezocine group (group D) .Twenty-four normal rats were chosen and served as normal control group (group C) .In group D , dezocine 2.52 mg/kg was injected intramuscularly once a day for 7 consecutive days starting from 2nd week after STZ injection ,while the rats in DNP and C groups received the equal volume of normal saline .Paw withdrawl threshold (PWT) to mechanical stimulation was measured before dezocine injection (T0 ) ,and on 1st ,3rd ,5th and 7th days after dezocine injection (T1-4 ) and on 7th day after the end of dezocine injection (T5 ) .Twelve rats in each group were sacrificed after measurement of PWT at T4 ,and T5 .The lumbar segments of the spinal cord were removed for determination of NR2B protein expression (by immuno-histochemistry and Western blot ) and NR2B mRNA expression (by RT-PCR ) in the spinal dorsal horns .Results Compared with group C ,the PWT at T0-5 in group DNP and at T0 and T5 in group D was significantly decreased , and the expression of NR2B protein and mRNA at T4 ,5 in DNP group and at T5 in D group was up-regulated ( P0.05) . The PWT was significantly lower at T0 and T5 ,and the expression of NR2B protein and mRNA was higher at T5 than at T4 in group D ( P<0.05 ) .Conclusion Dezocine can effectively relieve DNP in rats and inhibition of NR2B expression in the spinal dorsal horns is involved in the mechanism .