脊髓神经元ERK5/CREB信号通路在吗啡依赖大鼠戒断反应中的作用

Role of spinal neuronal ERK5/CREB signaling pathway in withdrawal responses in morphine-dependent rats

目的 评价脊髓神经元细胞外信号调节蛋白激酶5/cAMP反应元件结合蛋白（ERK5/CREB）信号通路在吗啡依赖大鼠戒断反应中的作用.方法 取鞘内置管成功的成年雄性SD大鼠96只,体重200～ 250 g,采用随机数字表法,将其分为4组（n=24）：正常对照组（A组）、吗啡戒断组（B组）、二甲基亚砜＋吗啡戒断组（C组）和ERK5抑制剂BIX02188＋吗啡戒断组（D组）.B组、C组和D组皮下注射吗啡,第1天剂量10 mg/kg,第2～5天剂量每天增加10 mg/kg,第6天剂量50 mg/kg,建立大鼠吗啡依赖模型,A组给予等容量生理盐水.B组和D组于末次注射吗啡后4h腹腔注射纳洛酮4mg/kg,建立吗啡戒断模型,D组给予纳洛酮前1h鞘内注射BIX02188 10 μg,C组给予等容量二甲基亚砜.给予纳洛酮后1h内进行戒断反应评分和戒断反应诱发痛觉过敏评分.处死大鼠,取L4.5节段脊髓组织,测定CREB和磷酸化CREB（p-CREB）的表达水平.结果 与A组比较,B组、C组和D组戒断反应评分和痛觉过敏评分升高,脊髓p-CREB表达上调（P＜0.05）;与B组比较,D组戒断反应评分和痛觉过敏评分降低,脊髓p-CREB表达下调（P＜0.05）,C组上述指标差异无统计学意义（P＞0.05）.结论 脊髓神经元ERK5/CREB信号通路参与了吗啡依赖大鼠戒断反应.

Objective To evaluate the role of spinal neuronal extracellular signal-regulated protein kinases 5/cAMP response element binding protein （ERK5/CREB） signaling pathway in withdrawal responses in morphinedependent rats.Methods Ninety-six adult male Sprague-Dawley rats in which intrathecal catheters were successfully placed,weighing 200-250 g,were randomly divided into 4 groups （n =24 each）：normal control group （group A）,morphine withdrawal group （group B）,dimethyl sulfoxide （DMSO） ＋ morphine withdrawal group （group C） and ERK5 inhibitor BIX02188 ＋ morphine withdrawal group （group D）.Morphine dependence （MD） was induced by increasing doses of subcutaneous morphine for 6 days.The initial dose of morphine was 10 mg/kg once a day and was increased by 10 mg/kg once a day from 2nd to 5th days until 50 mg/kg on 6th day in B,C and D groups.Morphine withdrawal response （MW） was induced by intraperitoneal naloxone 4 mg/kg at 4 h after last morphine administration in B,C and D groups.In addition,BIX02188 10 μg and 1% DMSO 10 μl were injected intrathecally at 1 h before naloxone injection in D and C groups,respectively.MW and morphine withdrawal-induced hyperalgesia were scored.The rats were then sacrificed after hyperalgesia was scored and the spinal cord was removed for determination of CREB and phosphorylated CREB （p-CREB） expression.Results Compared with group A,MW and hyperalgesia scores were significantly increased and the expression of p-CREB was up-regulated in B,C and D groups.Compared with group B,MW and hyperalgesia scores were significantly decreased and the expression of p-CREB was down-regulated in D group,and no significant change was found in group C.Conclusion The spinal neuronal ERK5/CREB signaling pathway is involved in withdrawal responses in morphine-dependent rats.