Enhancement of Behavioral Sensitization,Anxiety-Like Behavior,and Hippocampal and Frontal Cortical CREB Levels Following Cocaine Abstinence in Mice Exposed to Cocaine during Adolescence

Adolescence has been linked to greater risk-taking and novelty-seeking behavior and a higher prevalence of drug abuse and risk of relapse. Decreases in cyclic adenosine monophosphate response element binding protein (CREB) and phosphorylated CREB (pCREB) have been reported after repeated cocaine administration in animal models. We compared the behavioral effects of cocaine and abstinence in adolescent and adult mice and investigated possible age-related differences in CREB and pCREB levels. Adolescent and adult male Swiss mice received one daily injection of saline or cocaine (10 mg/kg, i.p.) for 8 days. On day 9, the mice received a saline injection to evaluate possible environmental conditioning. After 9 days of withdrawal, the mice were tested in the elevated plus maze to evaluate anxiety-like behavior. Twelve days after the last saline/cocaine injection, the mice received a challenge injection of either cocaine or saline, and locomotor activity was assessed. One hour after the last injection, the brains were extracted, and CREB and pCREB levels were evaluated using Western blot in the prefrontal cortex (PFC) and hippocampus. The cocaine-pretreated mice during adolescence exhibited a greater magnitude of the expression of behavioral sensitization and greater cocaine withdrawal-induced anxiety-like behavior compared with the control group. Significant increases in CREB levels in the PFC and hippocampus and pCREB in the hippocampus were observed in cocaine-abstinent animals compared with the animals treated with cocaine in adulthood. Interestingly, significant negative correlations were observed between cocaine sensitization and CREB levels in both regions. These results suggest that the behavioral and neurochemical consequences of psychoactive substances in a still-developing nervous system can be more severe than in an already mature nervous system.     

CREB信号通路在神经系统中的调控及功能

cAMP应答元件结合蛋白(cAMP response element binding protein,CREB)在神经元生成、突触可塑性及学习记忆等方面都具有重要的调节作用,这使得与CREB信号通路相关的分子成为较受关注的神经系统疾病干预的药物靶点.本文概述了CREB的基本构成、相关信号通路、其目的基因表达调控及其在阿尔茨海默病(Alzheimer’s disease,AD)中的作用.     

cAMP反应元件结合蛋白介导磷酸化细胞外信号调节激酶在神经病理性痛形成中的作用

采用行为学、免疫组织化学和Western blot方法,观察鞘内注射细胞外信号调节激酶(extracellular signal-regulate kinase,ERK)信号转导通路阻滞剂对慢性压迫性损伤(chronic constriction injury,CCI)大鼠痛行为及脊髓背角内磷酸化cAMP反应元件结合蛋白(phosphorylated cAMP response-element binding protein,pCREB)和Fos表达变化的影响,探讨ERK／CREB转导通路在神经病理性疼痛中的作用。结果表明,CCI可明显增加双侧脊髓背角pCREB、损伤侧脊髓背角浅层Fos阳性神经元表达,以CCI后3与5d时尤为显著。鞘内沣射促分裂原活化蛋白激酶激酶(mitogen-activated protein kinase kinase,MEK)阻滞剂U0126及ERK反义寡核苷酸在减轻大鼠痛行为的同时,能明显抑制双侧脊髓背角内pCREB的表达,同时,Fos阳性神经元的表达也明显减少。大鼠痛行为及脊髓背角pCREB和Fos的表达在时相上一致。上述结果提示pCREB参与pERK介导的神经病理性疼痛。     

Differential expression of K+ channel mRNAs in the rat brain and down-regulation in the hippocampus following seizures.

K+ channels are major determinants of membrane excitability. Differences in neuronal excitability within the nervous system may arise from differential expression of K+ channel genes, regulated spatially in a cell type-specific manner, or temporally in response to neuronal activity. We have compared the distribution of mRNAs of three K+ channel genes, Kv1.1, Kv1.2, and Kv4.2 in rat brain, and examined activity-dependent changes following treatment with the convulsant drug pentylenetetrazole. Both regional and cell type-specific differences of K+ channel gene expression were found. In addition, seizure activity caused a reduction of Kv1.2 and Kv4.2 mRNAs in the dentate granule cells of the hippocampus, raising the possibility that K+ channel gene regulation may play a role in long-term neuronal plasticity.     

转录调节因子TORCs的研究进展及其参与神经保护作用的展望

随着基础研究的深入,人们对于cAMP反应元件结合蛋白（cAMP response element binding protein,CREB）及其家族的功能了解越来越多。在多种细胞中,这些转录因子作为效应分子介导细胞外环境变化所引起基因表达和长时程生理功能改变。存神经系统,许多胞外信号,包括细胞膜去极化、膜受体通道开放以及神经损伤等,都可以引起CREB及其家族成员分子的激活,从而引起CREB依赖的基因转录。CREB的激活及其下游綦因的转录在多种复杂的发育、神经可塑性和病理过程中都具有十分重要的作用。TORCs（transducers of regulated CREB）是新近被发现的一类CREB的共激活列子,但其对CREB的精确调控机制尚不明确。目前已知TORCs可以促进CREB依赖的基因转录,并且这种增强作用不依赖于CREB丝氨酸133位点的磷酸化,而足增加CREB和其辅助因子的结合,从而实现其下游基因在启动予水平的活性增加。在神经系统的各类疾病中,CREB对于促进神经元存活、再生、细胞修复等过程具有十分重要的作用。因此,作为CREB的共激活因子,TORCS在神经损伤修复中也具有潜在作用,本文主要针对新近发现的CREB共激活因了TORCs进行简要的文献综述和其在神经保护作用中的展望。