Effect of morphine exposure in late pregnancy on expression of NR2B in nucleus accumbens of off-spring rats / 中华麻醉学杂志

ABSTRACT

Objective To evaluate the effect of morphine exposure in the late pregnancy on the expression of 2B subunit-containing N-methyl-D-aspartate receptor (NR2B) in the nucleus accumbens of offspring rats.Methods Forty-eight Sprague-Dawley rats at 14 days of gestation,aged 16-20 weeks,weighing 400-600 g,were equally and randomly divided into control group (group C) and morphine group (group M).In group M,morphine was administered subcutaneously twice a day (900 a.m.and 500 p.m.) in the initial dose of 2 mg/kg followed by daily increment of 1 mg/kg until 6 mg/kg.The equal volume of normal saline was given instead of morphine in group C.Fifty offspring rats with similar body weight were selected from the two groups,and conventionally fed for 8 weeks.Thirty offspring rats were further selected,morphine 3 mg/kg was injected subcutaneously for 7 consecutive days,and then the rats underwent the conditioned place preference test to monitor the effect.The time spent in drug-paired side (gray area) was recorded at 24 h after the test.Ten offspring rats selected were sacrificed after the test,and the brain was removed.The nucleus accumbens was isolated for detection of the expression of NR2B by immunohistochemistry and Western blot.Results Compared with group M,the time spent in drug-paired side (gray area) was significantly prolonged,and the expression of NR2B in the nucleus accumbens was up-regulated in group C (P＜0.05).Conclusion The mechanism by which morphine exposure in the late pregnancy causes susceptibility to morphine addiction is associated with up-regulation of NR2B expression in the nucleus accumbens of offspring rats.