吗啡依赖大鼠中脑远位触液神经元ERK5活性的变化

Changes in activity of extracellular signal-regulated kinase 5 in distal cerebrospinal fluid contacting neurons in mid-brain of morphine dependent rats

目的 评价吗啡依赖大鼠中脑远位触液神经元细胞外信号调节蛋白激酶5（ERK5）活性的变化.方法 成年雄性SD大鼠48只,体重230 ～ 270 g,采用随机数字表法,将其分为2组（n=24）：对照组（A组）和吗啡依赖组（B组）.皮下注射吗啡,每天2次,连续5 d,建立大鼠吗啡依赖模型.每日剂量为：首日10 mg/kg,第2～5天分别为20、30、40和50 mg/kg.A组皮下注射等容量生理盐水.吗啡依赖模型制备的第3天上午,经侧脑室注射30％霍乱毒素亚单位B与辣根过氧化物酶复合物（CB-HRP）3 μl,用于标记远位触液神经元.于末次皮下注射吗啡后4h,取中脑远位触液神经元所在节段组织,采用免疫荧光法计数CB-HRP阳性神经元、磷酸化ERK5（p-ERK5）阳性神经元及CB-HRP/p-ERK5阳性神经元.结果 与A组相比,B组中脑p-ERK5阳性神经元计数和CB-HRP/p-ERK5阳性神经元计数升高（P＜0.05）,CB-HRP阳性神经元计数差异无统计学意义（P＞0.05）.结论 中脑远位触液神经元ERK5活性增强可能参与了大鼠吗啡依赖的形成.

Objective To evaluate the changes in the activity of extracellular signal-regulated kinase 5 （ERK5） in the distal cerebrospinal fluid contacting neurons （CSF-CNs） in the mid-brain of morphine dependent rats.Methods Forty-eight male adult Sprague-Dawley rats weighing 230-270 g,were randomly divided into 2 groups （n =24 each） using a random number table：control group （group A） and morphine dependence group （group B）.Morphine dependence was induced by increasing doses of subautaneous morphine for 5 consecutive days.The initial dose of morphine was 10 mg/kg twice a day and was increased by 10 mg/kg everyday until 50 mg/kg on 5th dav.The equal volume of normal saline was injected subcutaneously instead of morphine in group A.On 3rd day after morphine dependence was induced,the distal CSF-CNs in the mid-brain was labeled with 30% cholera toxin subunit B and horseradish peroxidase compound （CB-HRP） 3 μl injected in the lateral cerebral ventricle in the morning.At 4 h after the last injection of morphine,the segments in which CSF-CNs were located were removed,and CB-HRP positive neurons,phosphor-ERK5 （p-ERK5） positive neurons and CB-HRP/p-ERK5 positive neurons were counted.Results Compared with group A,the number of p-ERK5 and CB-HRP/p-ERK5 positive neurons in the mid-brain was significantly increased （P 〈 0.05）,and no significant change was found in CB-HRP positive neurons in group B （P 〉 0.05）.Conclusion The enhanced activity of ERK5 in the distal CSFCNs in the mid-brain may contribute to the development of morphine dependence in rats.