A role for corticotropin releasing factor and urocortin in behavioral responses to stressors

Corticotropin-releasing factor (CRF) and CRF-related neuropeptides have an important role in the central nervous system to mediate behavioral responses to stressors. CRF receptor antagonists are very effective in reversing stress-induced suppression and activation in behavior. An additional CRF-like neuropeptide, urocortin, has been identified in the brain and has a high affinity for the CRF-2 receptor in addition to the CRF-1 receptor. Urocortin has many of the effects of CRF but also is significantly more potent than CRF in decreasing feeding in both meal-deprived and free-feeding rats. In mouse genetic models, mice over-expressing CRF show anxiogenic-like responses compared to wild-type mice, and mice lacking the CRF-1 receptor showed an anxiolytic-like behavioral profile compared to wild-type mice. Results to date have led to the hypothesis that CRF-1 receptors may mediate CRF-like neuropeptide effects on behavioral responses to stressors, but CRF-2 receptors may mediate the suppression of feeding produced by CRF-like neuropeptides. Brain sites for the behavioral effects of CRF include the locus coeruleus (LC), paraventricular nucleus (PVN) of the hypothalamus, the bed nucleus of the stria terminalis (BNST), and the central nucleus of the amygdala. CRF may also be activated during acute withdrawal from all major drugs of abuse, and recent data suggest that CRF may contribute to the dependence and vulnerability to relapse associated with chronic administration of drugs of abuse. These data suggest that CRF systems in the brain have a unique role in mediating behavioral responses to diverse stressors. These systems may be particularly important in situations were an organism must mobilize not only the pituitary adrenal system, but also the central nervous system in response to environmental challenge. Clearly, dysfunction in such a fundamental brain-activating system may be the key to a variety of pathophysiological conditions involving abnormal responses to stressors such as anxiety disorders, affective disorders, and anorexia nervosa.     

Long-lasting increase in the set point for cocaine self-administration after escalation in rats

Rationale: When access time to a continuous schedule of drug self-administration is restricted, animals tend to limit intake to a certain level over time and across doses. This observation suggests an endogenous constraint or set point that determines the individual’s preferred level of pharmacological effects. Objectives: To assess whether the transition to increased levels of drug intake is associated with a change in set point. Methods: Two groups of rats were trained on a 1-h continuous schedule of cocaine self-administration (250 μg/injection), after which access to cocaine was increased to 6 h in one group (Long Access or LgA rats) or kept to 1 h in the other group (Short Access or ShA rats). After 22 sessions on this regimen, different doses of cocaine were tested (31.25, 62.5, 125, and 250 μg/injection). For each dose, the post-response time-out period was reduced to 4 s to reduce any temporal limitations on self-injections and subjects were tested several times. Results: In LgA rats, the first hour intake escalated over time and eventually reached a level 200% greater than that of ShA rats. Though all rats maintained relatively constant intake across doses, LgA rats took nearly two times as much cocaine than ShA rats. When access to cocaine for LgA rats was reduced to 1 h, intake returned very slowly toward pre-escalation levels but was still elevated even after 2 months of reduced availability. Conclusions: These data suggest that the transition to escalated levels of intake is associated with a long-lasting change in cocaine set point. Received: 12 February 1999 / Final version: 21 May 1999     

Heroin self-administration in dependent Wistar rats: increased sensitivity to naloxone

  Rationale: Non-dependent and dependent opiate users appear to be driven by two distinct motivational factors: the primary reinforcing properties of the drug, and the negative reinforcing effects associated with relieving the negative affective component of opiate withdrawal in the dependent state. Objective: To investigate the motivational significance of opioid dependence on heroin self-administration (HSA) in rodents. Methods: Rats were trained to self-administer heroin intravenously (0.06 mg/kg per infusion; FR1), and opiate dependence was induced by subcutaneous implantation of two morphine (75 mg base) pellets.Rats in a non-dependent control group received placebo pellets. Three days after pellet implantation, HSA was resumed in daily 3-h sessions until baseline criteria were met and testing was conducted with subcutaneous injections of vehicle or naloxone (0, 0.003, 0.01, 0.03 mg/kg) 115 min into the session. Results: Morphine-dependent rats significantly increased HSA upon 0.01 mg/kg naloxone treatment, but decreased response rates at 0.03 mg/kg. Placebo pellet-implanted rats increased heroin intake at the 0.01 and 0.03 mg/kg doses. In a second experiment, the HSA session was shortened to 1 h and the training dose reduced to 0.03 mg/kg per infusion in new groups of animals. HSA in placebo pellet-implanted rats was increased only following the highest dose of the antagonist, while dependent rats were still affected by naloxone doses of 0.003–0.03 mg/kg. When subjected to a progressive-ratio schedule (experiment 3), breaking point values in dependent animals were 198% above baseline. Conclusions: The present study supports the hypothesis that dependence-induction by morphine-pellet implant in rats resulted in increased sensitivity to very small naloxone doses, as measured by changes in HSA. Taken together, these data suggest that opiate dependence, as measured by changes in sensitivity to naloxone, is a continuum which can contribute to the motivational state of drug-seeking. Received: 5 June 1998 / Final version: 21 December 1998     

Desmethylimipramine attenuates cocaine withdrawal in rats

Depression and anhedonia are two major symptoms of cocaine withdrawal in humans. Hence, pharmacological treatments effective in depression might also alleviate the symptoms of cocaine withdrawal. In the present study, the effects of acute and repeated administration of a tricyclic antidepressant, desmethylimipramine (DMI), were investigated in naive and cocaine-withdrawing rats. An animal model of cocaine withdrawal was used that employs the elevation in intracranial self-stimulation (ICSS) thresholds following the termination of prolonged periods of cocaine self-administration as a measure of an animal's anhedonic state. The influence of chronic DMI treatment on-adrenergic receptor binding and affinity was also correlated with the behavioral signs of cocaine withdrawal. Neither acute nor repeated DMI treatment influenced reward functions in rats that were not undergoing cocaine withdrawal. However, repeated DMI treatment significantly down-regulated-adrenergic receptors, and shortened the duration of the post-cocaine anhedonia (elevation in thresholds). Furthermore, the magnitude of the-adrenergic receptor down-regulation correlated significantly with the degree of effectiveness of DMI treatment in reversing the post-cocaine anhedonia. However, chronic DMI treatment did reduce the amount of cocaine self-administered by the animals. The reversal of the post-cocaine anhedonia in this animal model of cocaine withdrawal by chronic DMI treatment demonstrates the potential usefulness of the model in identifying new pharmacotherapies for cocaine withdrawal. In addition, the results indicate that tricyclic antidepressants may be able to ameliorate some of the symptoms of cocaine withdrawal.     

丹参素胶囊活血化瘀作用的实验研究

目的：研究丹参素胶囊对大鼠血小板聚集性和血液流变学及血栓形成的影响。方法：以ADP为诱导剂，观察其对体外血小板聚集率的作用；采用电刺激法，测定闭塞性血栓形成的时间；用冰水刺激制备“血瘀”模型，检测主要流变学指标。结果：丹参素胶囊能明显抑制由ADP诱导的大鼠血小板体外聚集活性，延长电刺激大鼠颈总动脉后血栓形成时间，降低“血瘀”大鼠全血粘度、血浆粘度、红细胞压积、红细胞电泳时间、卡松屈服应力以及红细胞聚集指数，改善机体血液流变性。结论：丹参素胶囊能明显降低血液“浓、粘、聚、凝”状态，具有良好的活血化瘀作用。     

散发内淋巴囊瘤VHL基因位点微卫星标志杂合性丢失的研究

目的 探讨散发内淋巴囊瘤发病与VHL基因异常之间的关系。方法 采用组织微切割技术和多聚酶链式反应等方法对3例散发内淋巴囊瘤肿瘤细胞VHL基因位点染色体微卫星标志的杂合性丢失进行分析。结果 3例散发内淋巴囊瘤中有2例发生VHL基因位点微卫星标志的杂合性丢失,进一步的研究证实,该两例肿瘤细胞中分别存在着VHL基因第二外显子的异常。结论 VHL基因的异常导致其功能改变不但是VHL的致病原因,而且是散发性内淋巴囊瘤发病的重要的基因遗传学基础。     

对甲磺酰基苯乙烯环酮类衍生物的合成及抗炎活性

目的寻找新型高效低毒的非甾体抗炎药。方法合成对甲磺酰基苯乙烯环酮类衍生物，用二甲苯致小鼠耳肿胀模型和角叉菜胶致大鼠足跖肿胀模型评价其抗炎活性，并考察连续经口给药对大鼠胃肠道（GI）的影响。结果合成了9个新化合物（ZA_1-9），结构经IR，¹HNMR，MS和元素分析确证。小鼠试验表明ZA_3,5-9的抗炎活性与双氯芬酸钠(DC)和罗非昔布(RC)相当(P>0.05)，大鼠试验显示ZA_3,7,8的抗炎活性与DC和RC相当(P>0.05)， ZA₆的抗炎作用显著强于DC和RC(P<0.05)，ZA_3,5-9对GI损伤显著小于DC (P<0.05，P<0.01)，与RC相当(P>0.05)。结论对甲磺酰基苯乙烯环酮类衍生物的抗炎作用较强，GI不良反应小，值得进一步研究。     

自发性高血压大鼠血、尿III型前胶原水平变化及氯沙坦的干预作用

目的　探讨自发性高血压大鼠 (spontaneouslyhypertensiverat ,SHR)血、尿Ⅲ型前胶原 (ProcollagenⅢ ,PCⅢ )与早期肾脏损害的关系。方法　检测SHR及氯沙坦干预后血、尿PCⅢ水平。 14周龄雄性SHR16只随机分为高血压组和氯沙坦治疗组 (氯沙坦灌胃 3 0mg·kg-1·d-1)各 8只 ,14周龄雄性Wistar -kyoto大鼠 (WKY) 8只为正常对照组 ,16周后 ,放免法检测血、尿PCⅢ、尿微量白蛋白 (microalbumin ,ALB)及血、尿 β2 -微球蛋白 ( β2 -microglobin ,β2 -MG)。结果　SHR组尿PCⅢ、尿ALB及血、尿 β2 -MG水平明显高于WKY组 (P <0 0 5 ) ,三组血PCⅢ水平无显著差异 (P >0 0 5 )。氯沙坦可显著降低SHR组尿PCⅢ、尿 β2 -MG及尿ALB水平 ( P<0 0 5 )。血、尿PCⅢ无相关性 (r =0 2 2 6,P <0 0 5 )。尿PCⅢ与尿 β2 -MG(r =0 813 ,P <0 0 1)、尿ALB(r =0 5 60 ,P <0 0 1)、收缩压 (r =0 694,P <0 0 1)呈正相关。结论　SHR组尿PCⅢ、尿 β2 -MG、尿ALB水平升高 ,可一定程度反映高血压早期肾脏损害。氯沙坦可降低SHR血压、尿PCⅢ、尿 β2 -MG、尿ALB水平 ,对高血压肾脏有保护作用     

新生儿缺氧缺血性心脏损害早期诊疗的预后探讨

目的:研究新生儿缺氧缺血性心脏损害(HIM)早期诊断和及早微量多巴胺治疗对HIM预后的影响,探讨改善预后的措施。方法:对63例窒息新生儿48 h肌酸激酶同功酶(CK-MB)及心电图QT间期弥散度(QTcd)明显异常的HIM患儿及早微量多巴胺治疗,1-2周后再复查并与32例无窒息新生儿对照比较。结果:HIM组与对照组比较患儿发病48 h内CK-MB及QTcd均明显升高(P<0.001),经及早微量多巴胺治疗等措施1-2周后HIM患儿CK-MB及QTcd均显著下降,而产后缺氧组较胎儿期缺氧组下降更明显(P<0.005),且胎儿期缺氧组并发症多,预后差(P<0.005)。结论:CK-MB及QTcd相结合可作为HIM早期诊断指标,及早微量多巴胺治疗等措施,对改善预后意义重大。