CCK-8对吗啡成瘾大鼠戒断症状及尾核内c-jun蛋白表达的影响

目的从行为学、形态学角度,初步研究了八肽胆囊收缩素(CCK-8)对吗啡成瘾大鼠戒断症状及尾核(Cd)内原癌基因c-jun蛋白表达的影响。方法采用动物行为学评估和免疫组化的方法,观察吗啡成瘾大鼠Cd内注入CCK-8(10mg.L-1,1μl)对c-jun蛋白表达和戒断症状的影响。结果①吗啡成瘾组大鼠戒断症状与生理盐水对照组大鼠行为学相比有差异;②吗啡成瘾大鼠在戒断24h时,Cd内注入CCK-8可使戒断症状降低,在戒断40h时戒断症状总分最明显;③单纯吗啡成瘾组大鼠Cd内c-jun蛋白表达与生理盐水对照组大鼠相比下降,而注入CCK-8后c-jun蛋白的表达上升。结论①成功建立吗啡成瘾大鼠模型;②Cd内注入CCK-8可使吗啡成瘾大鼠的戒断症状明显减少;③Cd内注射CCK-8可提高c-jun蛋白的表达。提示CCK-8能调控吗啡成瘾大鼠戒断症状的产生及Cd内c-jun蛋白的表达。     

侧脑室注射内吗啡肽-1对麻醉大鼠血压的影响

目的　观察侧脑室注射内吗啡肽-1(EM-1)对麻醉大鼠血压的影响,并初步探讨其作用机理。方法　侧脑室埋植导管给药,颈动脉插管测血压。结果　icv EM-1剂量依赖、纳洛酮敏感地降低麻醉大鼠的血压。icv或iv酚妥拉明、普萘洛尔和iv L-NNA对EM-1引起的血压降低反应无影响;给予阿托品(icv 25 μg·kg^-1 ;或iv 50 μg·kg^-1)和切断双侧迷走神经减弱EM-1引起的血压降低反应。结论　icv EM-1可引起麻醉大鼠血压降低;此效应由阿片受体介导,有中枢M受体的参与,通过兴奋迷走神经所致     

应激和环境对吗啡暴露大鼠的电生理和行为学影响的研究

目的:研究平台应激、急性吗啡暴露对4周龄和10周龄♂W istar大鼠海马CA1区突触可塑性及空间记忆的影响以及研究丰富环境对大鼠学习记忆、吗啡诱导的条件性位置偏爱(cond itioned p lace preference,CPP)及海马CA1区突触可塑性的影响。方法:电生理实验(在体和离体)和行为学方法(水迷宫和CPP实验),统计采用方差分析(ANOVA)和t检验。结果与结论:(1)慢性应激和/或急性吗啡暴露分别对4周龄和10周龄这两个年龄段的LTP和LTD具有不同作用,存在明显的年龄差异。(2)急性平台应激损害4周龄和10周龄大鼠的记忆,但年龄差异没有显著性;慢性平台应激对10周龄大鼠记忆起易化作用,对4周龄没有明显的影响。(3)急性吗啡暴露(2 mg.kg-1)对4周龄大鼠的记忆有损害作用,而对10周龄大鼠的记忆没有影响。(4)急性应激加吗啡损害了4周龄大鼠的记忆保持,而对10周龄大鼠的记忆保持无影响;慢性应激加吗啡对4周龄大鼠的记忆保持无影响,对10周龄大鼠的记忆保持有易化作用。(5)丰富环境可以增强大鼠的空间学习和记忆能力,增强了吗啡诱导的CPP可能与学习和记忆能力的提高有关;同时,丰富环境对吗啡依赖所致的突触可塑性的损害有保护作用。丰富环境能逆转早期应激所产生的对学习记忆和突触可塑性的损害。     

丝瓜叶成分对脑缺血大鼠学习记忆障碍及皮层体感诱发电位的影响

目的:研究丝瓜叶成分L-6a 和L-10 对脑缺血大鼠学习记忆障碍及皮层体感诱发电位(SEP) 的影响。方法:用脑缺血大鼠模型,侧脑室注射(icv)给药,以穿梭箱主动回避反应(AAR) 测定学习记忆行为;用SYD₄₂₂₈ 型生理实验系统测定皮层体感诱发电位。结果:L-6a 0-5 mg·kg^-1 显著促进脑缺血大鼠AAR的获得;0-25 mg·kg^-1 时,无明显影响;L-6a 0-5 及0-25 mg·kg^-1 均显著延缓AAR的消退;脑缺血后,L-6a(0-5 mg·kg^-1) 也减缓SEP波幅下降及其潜伏期延长;脑缺血再通后,L-6a 和L-10(0-5 mg·kg^-1)均加大SEP振幅增高,缩短其潜伏期。结论:L-6a 有显著促进脑障碍大鼠脑功能恢复的作用。     

侧脑室注射八肽胆囊收缩素及其受体拮抗剂对吗啡依赖大鼠戒断症状的影响

目的观察侧脑室给予八肽胆囊收缩素(CCK-8)及其受体拮抗剂慢性干预对吗啡依赖大鼠戒断症状的影响,并在体外观察CCK-8对μ阿片受体结合反应的影响,初步探讨CCK-8对吗啡依赖过程的影响及其相关受体机制。方法建立大鼠吗啡依赖及纳络酮催促戒断模型,侧脑室注射CCK-8及CCK1受体拮抗剂devazepide、CCK2受体拮抗剂LY-288,513慢性干预,观察其对戒断症状的影响;应用放射配基结合实验体外检测CCK-8对μ阿片受体结合特征的影响。结果①吗啡注射前10 min侧脑室注射CCK-8和CCK受体拮抗剂devazepide、LY-288,513慢性干预均能降低吗啡依赖大鼠的戒断症状评分,并可明显改善体重下降、跳跃、齿颤、流涎等戒断症状,与戒断组相比差异均有显著性(P<0.01);②10-8～10-6 mol.L-1 CCK-8可以剂量依赖性地抑制大鼠脑组织中μ阿片受体与其配基的结合(P<0.01),降低μ阿片受体结合反应的Bmax值,而对Kd值无影响;且此抑制作用可被CCK1及CCK2受体拮抗剂翻转(P<0.01)。结论 CCK-8及其受体拮抗剂慢性干预均能减轻吗啡依赖大鼠戒断症状;CCK-8通过抑制μ阿片受体与其配基的结合,降低μ阿片受体的Bmax值,发挥其"抗阿片作用"。     

八肽胆囊收缩素及其受体拮抗剂对吗啡戒断大鼠脑内CaMK Ⅱ蛋白表达的影响

目的观察八肽胆囊收缩素(CCK-8)、CCK-1受体拮抗剂L-364,718及CCK-2受体拮抗剂LY-288,513对吗啡戒断大鼠额叶皮质、海马、纹状体细胞内钙/钙调蛋白依赖性的蛋白激酶Ⅱ(CaMKⅡ)表达的影响。方法建立吗啡依赖及纳洛酮催促戒断大鼠模型,观察CCK-8、L-364,718及LY-288,513对吗啡依赖大鼠戒断症状的影响;采用Western blot方法检测上述脑区CaMKⅡ蛋白表达的变化。结果①CCK-8、L-364,718及LY-288,513能明显改善吗啡依赖大鼠戒断症状的发生;②与盐水对照组相比,吗啡依赖组大鼠额叶皮质、海马、纹状体细胞内CaM KⅡ蛋白表达明显升高;纳洛酮催促戒断后上述脑区CaM KⅡ蛋白表达较吗啡依赖组均明显降低;③CCK-8、L-364,718及LY-288,513均使吗啡戒断大鼠额叶皮质、海马及纹状体内CaMKⅡ蛋白表达升高。结论 CaMKⅡ参与了吗啡依赖及戒断的形成,CCK-8及其受体拮抗剂抑制吗啡依赖大鼠戒断反应的机制可能与其对相关脑区CaMKⅡ蛋白表达的调节有关。     

Intrastriatal injection of hypoxanthine impairs memory formation of step-down inhibitory avoidance task in rats

The aim of this study was to investigate the effects of intrastriatal injection of hypoxanthine, the major compound accumulated in Lesch–Nyhan disease, on performance step-down inhibitory avoidance task in the rat. Male adult Wistar rats were divided in two groups: (1) saline-injected and (2) hypoxanthine-injected group. Treated-group received intrastriatal hypoxanthine solution 30min before training session (memory acquisition) or immediately after training session (memory consolidation) or 30 before test session (memory retrieval) on step-down inhibitory avoidance task. Results show that hypoxanthine administration caused significant memory impairment in all periods tested. These results show that intrastriatal hypoxanthine administration provoked memory process impairment of step-down inhibitory avoidance task, an effect that might be related to the cognitive memory alterations in Lesch–Nyhan patients.     

Intrastriatal injection of hypoxanthine impairs memory formation of step-down inhibitory avoidance task in rats

The aim of this study was to investigate the effects of intrastriatal injection of hypoxanthine, the major compound accumulated in Lesch–Nyhan disease, on performance step-down inhibitory avoidance task in the rat. Male adult Wistar rats were divided in two groups: (1) saline-injected and (2) hypoxanthine-injected group. Treated-group received intrastriatal hypoxanthine solution 30min before training session (memory acquisition) or immediately after training session (memory consolidation) or 30 before test session (memory retrieval) on step-down inhibitory avoidance task. Results show that hypoxanthine administration caused significant memory impairment in all periods tested. These results show that intrastriatal hypoxanthine administration provoked memory process impairment of step-down inhibitory avoidance task, an effect that might be related to the cognitive memory alterations in Lesch–Nyhan patients.     

Enduring effects of morphine pellets revealed by conditioned taste aversion

Morphine pellets (75 mg) were implanted subcutaneously in albino rats. Three days later, following 24 h without water, these rats (Group MSN) were given access to a saccharin solution for 30 min, then injected with naloxone hydrochloride. The classical abstinence signs, including wet dog shakes and weight loss, were noted in these subjects, but not in controls given placebo pellets and/or saline injections. In addition, when given an opportunity to drink either saccharine solution or water 24 h later, Group MSN rats drank significantly less saccharin than any of the control groups. Similar drinking patterns were found even when naloxone injection was delayed as long as 3 weeks after pellet implantation, when none of the classical abstinence signs were seen and serum levels of morphine and its metabolites were 100 times lower according to radioimmunoassay. This simple and objective technique is thus more sensitive as a measure of prior morphine exposure than any of the commonly used indices. The continued utility of a dependent-nondependent dichotomy is also examined in light of these and other findings.     

Pre-exposure to morphine and the attenuation of conditioned taste aversion in rats

Three experiments were done using male Wistar rats to determine whether the mechanisms underlying the attenuation of a conditioned taste aversion to morphine by pre-exposure to the drug were similar to those involved in the development of tolerance to the analgesic response to morphine. This was tested by determining whether the effect of pre-exposure on conditioned taste aversion was situation-specific. In Experiment 1 it was found that having different environments for the pre-exposure injections and for the conditioning injections of morphine had no effect on the attenuation of the taste aversion. This finding was replicated in Experiment 2 in which it was also found that the attenuation of the analgesic effect, tested for in the same animals, was specific to the environment in which repeated injections were given. It was concluded that the attenuation of conditioned taste aversion involved processes different from those responsible for the attenuation of the analgesic effect morphine. Experiment 3 showed that pairing the pre-exposure injections of morphine with one distinctive taste stimulus prevented the attenuation of the conditioned taste aversion to a second taste stimulus. These results suggest that different associative processes are responsible for the two types of attenuation.     

Isolation housing decreases the effectiveness of morphine in the conditioned taste aversion paradigm

Male Long Evans rats were obtained at 21 days of age and were housed in either an aggregated (four per double cage) or isolated (one per single cage) condition for 6 weeks. They were then placed on a fluid deprivation schedule that allowed them access to fluids for 20 min daily. This schedule was maintained for the remainder of the experiment. Following habituation, sensitivity to morphine-induced conditioned taste aversion (CTA) was compared in the differentially housed rats. On the 1st day and every 5 days thereafter the rats were presented with a 0.1% solution of sodium saccharin for the 20-min drinking period, followed immediately by an injection of morphine (0, 2.5, 5.0, 10.0, or 20.0 mg/kg). On intervening days they received water as the fluid. No drugs were given on these days. There was no difference in baseline saccharin consumption as a function of housing condition. In comparison with the isolated rats, the grouped animals were more sensitive to the CTA-inducing properties of low doses of morphine. These data strengthen the already existing evidence for the influence of the early housing environment on drug sensitivity and provide additional support for the conclusion that variability in response to a number of drugs of abuse can be reduced by environmental means. Possible mechanisms for the differences between isolation and aggregation housed rats are discussed.     

Tolerance to morphine stimulus control: role of morphine maintenance dose

Experiments assessed the development of tolerance to morphine stimulus control during treatment with selected maintenance doses of morphine. Separate groups of rats were trained to discriminate saline and either 3.2 mg/kg or 5.6 mg/kg morphine under fixed-ratio schedules of food delivery. Dose-response functions for generalization of morphine stimulus control were determined before, during, and after repeated treatment with selected doses of morphine. Similar experiments were performed with repeated pentobarbital treatment in order to assess the pharmacological selectivity of tolerance. Repeated treatment with saline, 3.2 mg/kg morphine, or twice daily injections of 17.8 mg/kg pentobarbital produced no tolerance to morphine stimulus control. In contrast, treatment with daily injections of 10 mg/kg or twice daily injections of 10 or 17.8 mg/kg morphine produced a dose-dependent increase in the dose of morphine required for stimulus control. The magnitude of tolerance to morphine stimulus control varied directly with the maintenance dose of morphine and was slightly greater for a lower than a higher morphine training dose. Termination of repeated treatment was followed by a return to initial sensitivity, without additional training. Tolerance to morphine stimulus control was not necessarily accompanied by tolerance to its rate-suppressing effects.     

Naltrexone-induced conditioned place aversion following a single dose of morphine in the rat

Limited preclinical research has been conducted investigating the motivational or "affective" properties of withdrawal from acute opioid dependence following a single morphine exposure. Therefore, the purpose of the present study was to pharmacologically characterize the motivational properties associated with naltrexone-precipitated withdrawal after a single injection of morphine using place conditioning. Conditioned place aversion was assessed using a biased two-compartment apparatus and procedure. Adult male Sprague-Dawley rats were given 15 min free access to the entire apparatus on day one to determine initial preferences. Beginning on the second day, combinations of either saline or morphine (1.0-10 mg/kg, s.c.) followed by naltrexone (0.003-3.0 mg/kg, s.c.) 3.75 h later were administered. Rats were then immediately confined to one compartment for 30 min. The next day, rats received the alternative treatment and were confined to the opposite compartment. Twenty-four hours later animals were tested again for 15 min while they had access to the entire apparatus. Morphine followed by naltrexone conditioned significant place aversion (CPA) with just one pairing. This effect was a function of the naltrexone and morphine doses. CPA was also dependent on morphine pretreatment time, with significant aversion only occurring 4 h after morphine pretreatment. Finally continuous morphine administration followed by a single injection of naltrexone resulted in CPA. These data extend the range of behavioral effects associated with antagonist-precipitated withdrawal from acutely administered morphine and suggest that place conditioning is an effective model in assessing motivational aspects of withdrawal from acute opioid dependence in rats.     

The effect of post-conditioning exposure to morphine on the retention of a morphine-induced conditioned taste aversion

In the following experiment, multiple injections of morphine sulfate following the acquisition of a morphine-induced taste aversion had no effect on the retention of the previously acquired aversion. Post-conditioning injections of morphine resulted in the development of physical dependence to morphine and led to a decrement in the ability of morphine to induce a subsequent aversion to a second novel taste. This failure of post-conditioning exposures to morphine to affect a previously acquired morphine-induced taste aversion even though tolerance to morphine had occured was discussed in the context of Rescorla's event-memory model of conditioning.