Browning Jeff L, Patel Tushar, Brandt Paul C, Young Keith A, Holcomb Leigh A, Hicks Paul B
Department of Psychiatry, Scott & White Memorial Hospital, Central Texas Veterans Health Care System, and Texas A & M University System Health Science Center College of Medicine, Temple, Texas, USA.
Biol Psychiatry. 2005 Mar 15;57(6):617-23. doi: 10.1016/j.biopsych.2004.12.002.
Mitogen-activated protein kinase (MAPK) signaling pathways respond to dopaminergic and serotonergic agents and mediate short- and long-term effects of intracellular signaling in neurons. Here we show that the antipsychotic agent, clozapine, selectively activates the MEK/ERK MAPK pathway, and inhibition of this pathway reverses clozapine's actions in the conditioned avoidance response (CAR) paradigm, a rodent behavioral assay of antipsychotic activity.
Phosphorylation patterns of MAPK pathway enzymes were determined by quantitative immunoblot analysis and immunohistochemistry of rat prefrontal cortex. Kinase inhibitors were used to assess the role of MAPK signaling pathways in mediating clozapine-induced suppression of CAR.
Clozapine administration selectively increased phosphorylation of MEK1/2 but had no effect on p38 or JNK phosphorylation. Pretreatment with the 5-HT2A agonist (+/-)-2,5-dimethoxy-4-iodoamphetamine hydrochloride blocked the clozapine-induced increase in MEK1/2 phosphorylation. Immunohistochemistry revealed that clozapine treatment elevated the number of cells in the prefrontal cortex positive for phosphoERK, the downstream substrate of MEK1/2. Prior administration of MEK1/2 inhibitors U0126 or Sl327, or ERK inhibitor 5-iodotubercidin, reversed suppression of CAR induced by clozapine, whereas administration of vehicle, JNK or p38 inhibitors (L-JNK-1 and SB203580, respectively) had no effect. Inhibition of kinases upstream to MEK1/2 (PI-3K, PKC, and CaMKII) by administration of LY294002, bisindolylmaleimide, or KN-62, respectively, also reversed clozapine-induced suppression of CAR.
These data support the hypothesis that the MEK/ERK signal transduction cascade participates in clozapine's antipsychotic actions.
丝裂原活化蛋白激酶（MAPK）信号通路对多巴胺能和5-羟色胺能药物产生反应，并介导神经元内信号传导的短期和长期效应。在此我们表明，抗精神病药物氯氮平选择性激活MEK/ERK MAPK信号通路，抑制该信号通路可逆转氯氮平在条件性回避反应（CAR）范式中的作用，CAR范式是一种用于抗精神病活性检测的啮齿动物行为学试验。
通过对大鼠前额叶皮质进行定量免疫印迹分析和免疫组织化学，确定MAPK信号通路酶的磷酸化模式。使用激酶抑制剂评估MAPK信号通路在介导氯氮平诱导的CAR抑制中的作用。
给予氯氮平选择性增加MEK1/2的磷酸化，但对p38或JNK的磷酸化无影响。用5-HT2A激动剂（±）-2,5-二甲氧基-4-碘苯丙胺盐酸盐预处理可阻断氯氮平诱导的MEK1/2磷酸化增加。免疫组织化学显示，氯氮平治疗使前额叶皮质中MEK1/2的下游底物磷酸化ERK阳性细胞数量增加。预先给予MEK1/2抑制剂U0126或Sl327，或ERK抑制剂5-碘结核菌素，可逆转氯氮平诱导的CAR抑制，而给予溶剂、JNK或p38抑制剂（分别为L-JNK-1和SB203580）则无作用。分别给予LY294002、双吲哚马来酰胺或KN-62抑制MEK1/2上游的激酶（PI-3K, PKC和CaMKII），也可逆转氯氮平诱导的CAR抑制。
这些数据支持MEK/ERK信号转导级联参与氯氮平抗精神病作用的假说。
