不同程度的性发作对成年大鼠空间学习记忆影响的研究

目的研究不同程度的性发作对成年大鼠空间学习记忆的影响。方法采用氯化锂和匹罗卡品联合诱导大鼠不同程度的癫模型(轻型和重型)。于造模后第6d给所有大鼠腹腔注射5-溴脱氧尿苷嘧啶(BrdU+)标记海马齿状回增殖的内源性神经前体细胞;用免疫组化方法观察各组大鼠注射BrdU+后第1d和第28d齿状回BrdU+阳性细胞数以及第28d的BrdU+/神经元核性蛋白(NeuN+)阳性细胞数及分布情况;利用Morris水迷宫评价大鼠的学习记忆功能。结果与正常组及轻型组比较,在各个时间点重型组海马齿状回BrdU+细胞数均增加(P<0.05),28d时BrdU+/NeuN+细胞数相应增多,但其占BrdU+细胞数的比例明显下降(P<0.05)。28d时重型组大鼠的学习记忆功能较正常组及轻型组明显下降(P<0.05)。结论严重的癫发作造成大鼠对空间学习记忆功能的损害,可能与其刺激大鼠海马齿状回内源性神经前体细胞增殖水平,抑制其分化为新生的成熟神经元有关。     

ERK1/2激活物Orexin-A对癫痫大鼠学习记忆及海马神经细胞增殖的影响

目的探讨ERK1/2激活物orexin-A(OXA)对戊四氮(PTZ)点燃大鼠空间学习记忆功能及海马齿状回神经细胞增殖的影响。方法 60只大鼠随机分为对照组、PTZ+生理盐水(NS)组、PTZ+OXA组、PTZ+U0126组和PTZ+U0126+OXA组,每组12只。采用腹腔注射PTZ(35 mg/kg)制模。制模后,对照组及PTZ+NS组大鼠注射8μl生理盐水,PTZ+OXA组大鼠注射8μl OXA,PTZ+U0126组注射8μl U0126,PTZ+U0126+OXA组注射8μl U0126和OXA 8μl。通过Morris水迷宫试验观察各组大鼠的空间学习记忆能力,并用BrdU腹腔注射和免疫荧光共聚焦技术检测海马齿状回区BrdU和BrdU/双皮质素(DCX)的阳性表达。结果 PTZ+NS组、PTZ+OXA组、PTZ+U0126组、PTZ+U0126+OXA组大鼠逃避潜伏期显著长于对照组(均P0.01)。PTZ+NS组、PTZ+U0126组及PTZ+U0126+OXA组大鼠逃避潜伏期显著长于PTZ+OXA组(P0.05~0.01)。与PTZ+NS组比较,PTZ+OXA组、PTZ+U0126+OXA组大鼠穿越平台象限的次数增加,平台所在象限的游泳时间延长(均P0.01);而PTZ+U0126组大鼠穿越平台象限的次数及平台所在象限的游泳时间均减少(均P0.01)。PTZ+U0126+OXA组大鼠穿越平台象限的次数显著少于、平台所在象限的游泳时间短于PTZ+OXA组(均P0.01)。PTZ+NS组、PTZ+U0126组及PTZ+U0126+OXA组大鼠海马齿状回区BrdU+/DCX+细胞数少于PTZ+OXA组(P0.05~0.01)。结论 OXA可通过促进齿状回颗粒细胞的再生改善癫痫大鼠的空间学习记忆能力,这可能与ERK1/2激活有关。     

卡马西平对匹罗卡品诱导成年癫间疒大鼠海马齿状回神经前体细胞增殖的影响

目的研究卡马西平对成年癫大鼠海马齿状回内源性神经前体细胞增殖的影响。方法采用氯化锂和匹罗卡品联合诱导大鼠癫模型,将癫大鼠随机分为癫对照组和癫卡马西平组,正常大鼠随机分为正常对照组和正常卡马西平组。癫对照组和正常对照组给以蒸馏水灌胃,同时癫卡马西平组和正常卡马西平组给予卡马西平灌胃。于灌胃后第6d腹腔注射5-溴脱氧尿苷嘧啶(BrdU)标记海马齿状回的内源性神经前体细胞的增殖情况;用免疫组化方法观察各组大鼠在注射BrdU后第1d、第7d齿状回BrdU阳性细胞数量的表达。结果①注射BrdU后第1d,癫对照组大鼠海马齿状回BrdU阳性细胞数较正常对照组明显增加(P<0.01),癫卡马西平组大鼠海马齿状回BrdU阳性细胞数较癫对照组减少(P<0.05);②注射BrdU后第7d,癫对照组大鼠海马齿状回BrdU阳性细胞数较正常对照组明显增加(P<0.01),癫卡马西平组大鼠海马齿状回BrdU阳性细胞数较癫对照组明显减少(P<0.05)。结论卡马西平抑制癫大鼠海马齿状回内源性神经前体细胞增殖。     

Orexin受体拮抗剂对睡眠剥夺的戊四氮致疒间大鼠癫疒间发作及脑组织病理学变化的影响

目的探讨orexin-1受体(OX1R)和orexin-2受体(OX2R)拮抗剂对睡眠剥夺(SD)的戊四氮(PTZ)致疒间大鼠癫疒间发作及脑组织病理学变化的影响。方法雄性Wistar大鼠48只,随机分为正常对照(NC)组、PTZ组、SD+PTZ(SD)组、SD+PTZ+二甲基亚砜(DMSO)组、SD+PTZ+OX1R拮抗剂SB334867(SB)组和SD+PTZ+OX2R拮抗剂TCS OX229(TCS)组。采用改良多平台SD法,SD前及SD 48 h分别给予相应组大鼠侧脑室注射DMSO、SB或TCS。SD 72 h给予各组腹腔注射PTZ 50 mg/kg诱导癫疒间发作;观察各组大鼠癫疒间发作的潜伏期、发作等级评分、发作持续时间及死亡率;应用常规染色法观察海马的病理学变化,免疫荧光法(BrdU标记)观察神经细胞增殖的变化。结果 (1)与PTZ组比较,SD组及DMSO组疒间性发作的潜伏期明显缩短,发作等级评分、持续时间及死亡率明显增加(均P<0.001),海马CA3区神经元损害加重,海马齿状回门区和颗粒细胞下层BrdU阳性细胞数显著增多(P<0.001);SD组与DMSO组间差异无统计学意义。(2)与SD组比较...     

Orexin受体拮抗剂对睡眠剥夺的戊四氮致(癎)大鼠癫(癎)发作及脑组织病理学变化的影响

目的 探讨orexin-1受体(OX1R)和orexin-2受体(OX2R)拮抗剂对睡眠剥夺(SD)的戊四氮(PTZ)致(癎)大鼠癫(癎)发作及脑组织病理学变化的影响.方法 雄性Wistar大鼠48只,随机分为正常对照(NC)组、PTZ组、SD+ PTZ( SD)组、SD+ PTZ+二甲基亚砜(DMSO)组、SD+ PTZ+ OX1R拮抗剂SB334867(SB)组和SD+ PTZ+ OX2R拮抗剂TCS OX229 (TCS)组.采用改良多平台SD法,SD前及SD 48 h分别给予相应组大鼠侧脑室注射DMSO、SB或TCS.SD 72 h给予各组腹腔注射PTZ 50 mg/kg诱导癫(癎)发作;观察各组大鼠癫(癎)发作的潜伏期、发作等级评分、发作持续时间及死亡率;应用常规染色法观察海马的病理学变化,免疫荧光法(BrdU标记)观察神经细胞增殖的变化.结果 (1)与PTZ组比较,SD组及DMSO组(癎)性发作的潜伏期明显缩短,发作等级评分、持续时间及死亡率明显增加(均P ＜0.001),海马CA3区神经元损害加重,海马齿状回门区和颗粒细胞下层BrdU阳性细胞数显著增多(P＜0.001);SD组与DMSO组间差异无统计学意义.(2)与SD组比较,SB组和TCS组大鼠(癎)性发作的潜伏期明显延长,发作等级评分、持续时间及死亡率明显下降(均P＜0.05),海马CA3区神经元损害明显减轻,齿状回门区和颗粒下层BrdU阳性细胞数减少(均P ＜0.05);TCS组的变化较SB组更显著(P＜0.05 ～0.01).结论 Orexin受体拮抗剂尤其是OX2R拮抗剂可通过减轻海马CA3区神经元的损害和抑制齿状回区细胞增殖减轻SD对PTZ诱导癫(癎)发作的不利影响.     

发育期癫大鼠移植骨髓源性神经干细胞对海马BDNF和bFGF表达的影响

目的将骨髓源性神经干细胞(BMSCs)移植到发育期癫大鼠海马区,观察大鼠海马脑源性神经营养因子(BDNF)和碱性成纤维生长因子(bFGF)表达的变化。方法选择21日龄发育期大鼠,分离大鼠骨髓基质细胞,在特定条件下培养使其诱导分化为神经干细胞(NSC)。建立戊四氮(PTZ)点燃癫大鼠模型,将BMSCs经侧脑室注射移植至癫大鼠海马区;侧脑室注射磷酸缓冲液(PBS)作为对照。分为4组(均n=8):对照组(无癫发作),PTZ致组(癫造模,无治疗),假手术组(癫+PBS侧脑室注射),治疗组(癫+NSC侧脑室注射)。于3、7和14 d处理后用免疫组化法检测大鼠海马区BDNF和bFGF表达。结果致组大鼠海马区(齿状回、CA1区)BDNF和bFGF表达较对照组增加(P0.05),治疗组海马区(齿状回、CA1区)BDNF和bFGF表达较假手术组也有所增加(P0.05)。结论 BMSCs移植可以增加PTZ致大鼠海马BDNF和bFGF表达,从而发挥对癫后脑损伤的保护作用。     

丰富环境促进颞叶癫(痫)大鼠神经发生及其机制的研究

目的 探讨丰富环境对颞叶癫(痫)大鼠齿状回新生细胞分化和存活的影响及其相关分子机制.方法 成年Wistar 大鼠随机分为4组:假手术组、丰富环境+假手术组、癫(痫)组、丰富环境+癫(痫)组,各组均n=15.大鼠侧脑室注射海人酸制作颞叶癫(痫)模型.丰富环境干预30 d后,应用免疫荧光技术观察大鼠海马齿状回的新生细胞分化和存活情况,用Western blot方法检测各组海马脑源性神经营养因子(BDNF)、cAMP应答元件结合蛋白(pCREB)、蛋白激酶A(PKA)表达水平.结果 丰富环境+假手术组、丰富环境+癫(痫)组齿状回新生细胞标记物(BrdU)和新生成熟神经细胞标记物(BrdU/NeuN)阳性细胞数分别多于假手术组、癫(痫)组(P＜0.05),而新生星形胶质细胞BrdU/GFAP阳性细胞数无统计学意义,并且丰富环境+假手术组、丰富环境+癫(痫)组海马BDNF和pCREB蛋白表达水平分别高于假手术组、癫(痫)组(P＜o.05),而PKA蛋白表达水平无增高.结论 丰富环境可能通过增强pCREB/BDNF通路促进成年颞叶癫(痫)大鼠海马齿状回的神经发生.     

卡马西平对成年癫大鼠海马齿状回BrdU/NeuN表达水平及其对空间记忆的影响

目的研究卡马西平对成年癫大鼠海马齿状回新生神经元的影响及其与空间记忆之间的关系。方法采用氯化锂和匹罗卡品联合诱导大鼠癫模型,利用5-溴脱氧尿苷嘧啶与神经元核性蛋白双标记观察海马齿状回内源性神经前体细胞分化为成熟神经元的情况;利用行为学分析评价大鼠的空间记忆。结果 (1)卡马西平可增加癫大鼠海马齿状回新生成熟神经元的数量(P<0.05);(2)卡马西平对癫大鼠的空间记忆有明显改善作用(P<0.01)。结论卡马西平增加癫大鼠海马齿状回新生成熟神经元形成,是其改善癫大鼠空间记忆的可能机制之一。     

老年大鼠脑出血后海马齿状回神经干细胞的增殖与分化

目的 观察老年大鼠脑出血后海马齿状回神经干细胞(NSCs)的增殖与分化,探讨脑出血后NSCs的变化规律.方法 制作老年大鼠脑出血模型,5-溴脱氧尿核苷(BrdU)腹腔注射标记增殖细胞,用免疫组化法检测大鼠海马齿状回BrdU、神经元核抗原(NeuN)、胶质纤维酸性蛋白(GFAP)阳性细胞数的变化.结果 正常组和假手术组老年大鼠海马齿状回均有少量BrdU阳性细胞,脑出血后大鼠各时间段的BrdU阳性细胞数目均较正常组和假手术组明显增加,7d组达到峰值后逐渐下降,28d组仍高于正常组和假手术组.正常老年大鼠海马齿状回可见少量BrdU/NeuN和BrdU/GFAP双标阳性细胞,脑出血后双标阳性细胞数较正常组明显增加.结论 脑出血后老年大鼠海马齿状回NSCs增殖明显,且可以向神经元和神经胶质细胞分化.     

丰富环境对成年颞叶癫大鼠认知功能及神经发生的影响

目的对成年颞叶癫大鼠进行丰富环境干预,探讨丰富环境是否能促进认知功能以及是否对齿状回的神经发生产生影响。方法将成年Wistar大鼠随机分为4组:假手术组、丰富环境+假手术组、癫组、丰富环境+癫组。丰富环境干预30 d后,应用Morris水迷宫实验进行学习记忆功能评价,并应用免疫荧光技术观察海马齿状回新生神经细胞的情况。结果一般线性重复变量分析示逃避潜伏期[F(3,36)=9.810,P0.05)]、上台前路程[F(3,36)=11.092,P0.05)],各组间差异有显著性;而游泳速度差异无显著性[F(3,36)=0.776,P0.05)]。丰富环境+假手术组海马齿状回DCX阳性细胞(新生神经细胞标志物)[(65.00±6.10)个]显著多于假手术组[(32.43±2.76)个](P0.05),癫组DCX阳性细胞[(21.30±2.97)个]较假手术组明显减少(P0.05);丰富环境+癫组DCX阳性细胞[(51.50±3.16)个]明显多于癫组(P0.05)。结论丰富环境有利于成年颞叶癫大鼠认知功能的恢复。     

The effect of antagonization of orexin 1 receptors in CA1 and dentate gyrus regions on memory processing in passive avoidance task

The hippocampal formation plays an essential role in associative learning like passive avoidance (PA) learning. It has been shown; orexin-containing terminals and orexin receptors densely are distributed in the hippocampal formation. We have previously demonstrated that antagonization of orexin 1 receptor (OX1R) in CA1 region of hippocampus and dentate gyrus (DG) impaired spatial memory processing. Although, there are few studies concerning function of orexinergic system on memory processing in PA task, but there is no study about physiological function of OX1R on this process. To address this, the OX1R antagonist, SB-334867-A, was injected into DG or CA1 regions of hippocampus and evaluated the influence of OX1R antagonization on acquisition, consolidation and retrieval in PA task. Our results show that, SB-334867-A administration into CA1 region impaired memory retrieval but not PA acquisition and consolidation. However, SB-334867-A administration into DG region impaired acquisition and consolidation but not PA memory retrieval. Therefore, it seems that endogenous orexins play an important role in learning and memory in the rat through OX1Rs.     

Pentylenetetrazol-induced seizures are exacerbated by sleep deprivation through orexin receptor-mediated hippocampal cell proliferation

Sleep deprivation has been shown to be an activator of seizures in clinical and animal studies. Orexin-A was speculated to be involved in the aggravation of seizures by sleep deprivation through the activation of its receptors: orexin-1 and orexin-2 receptor (OX1R and OX2R, respectively). Therefore, we aimed to investigate the effects of pre-treating sleep-deprived Wistar rats with the OX1R or OX2R antagonists, SB334867 (30 nM/kg) or TCS OX2 29 (30 nM/kg), respectively, followed by a convulsive dose of 50 mg/kg pentylenetetrazol administration (seizure induction), on seizure behavior, and hippocampal neurodegeneration and cellular proliferation. Our results revealed that treatment with SB334867 or TCS OX2 29 significantly prolonged the latency and reduced the duration of seizures, while also lowering the mortality rate in sleep-deprived rats exposed to pentylenetetrazol. In addition, SB334867 or TCS OX2 29 reduced the damage to hippocampal CA3 neurons and the number of bromodeoxyuridine-positive cells in the dentate gyrus (particularly in the hilus). Overall, the effect of TCS OX2 29 was greater than that of SB334867. Taken together, these data suggest that OX1R and OX2R antagonists may alleviate the damage of pentylenetetrazol-induced seizures that are exacerbated by sleep deprivation, and furthermore could be associated with a reduction of neuronal damage in the hippocampus and the inhibition of cellular proliferation in the dentate gyrus.     

Resuscitation therapy for traumatic brain injuryinduced coma in rats:mechanisms of median nerve electrical stimulation

In this study, rats were put into traumatic brain injury-induced coma and treated with median nerve electrical stimulation. We explored the wake-promoting effect, and possible mechanisms, of median nerve electrical stimulation. Electrical stimulation upregulated the expression levels of orexin-A and its receptor OX1 R in the rat prefrontal cortex. Orexin-A expression gradually increased with increasing stimulation, while OX1 R expression reached a peak at 12 hours and then decreased. In addition, after the OX1 R antagonist, SB334867, was injected into the brain of rats after traumatic brain injury, fewer rats were restored to consciousness, and orexin-A and OXIR expression in the prefrontal cortex was downregulated. Our findings indicate that median nerve electrical stimulation induced an up-regulation of orexin-A and OX1 R expression in the prefrontal cortex of traumatic brain injury-induced coma rats, which may be a potential mechanism involved in the wake-promoting effects of median nerve electrical stimulation.     

有氧训练对阿尔茨海默病模型大鼠海马神经细胞凋亡及再生的影响

目的:观察有氧训练对Aβ_25-35诱导的阿尔茨海默病（AD）大鼠海马神经细胞凋亡及再生的影响。方法:SD大鼠48只,随机分为3组（均n=16）:①假手术组（于大鼠侧脑室注射等量生理盐水+4周有氧训练）;②AD+有氧训练组(于大鼠侧脑室注射Aβ_25-35制作AD大鼠模型+4周有氧训练);③AD组(仅于大鼠侧脑室注射Aβ_25-35制作AD模型)。AD造模后第3天开始进行连续4周的无负重游泳训练,训练结束后各组大鼠分别行Morris水迷宫行为学检测认知行为能力、Hoechst染色观察海马神经细胞凋亡、BrdU/NeuN荧光双染观察齿状回（DG）区新生神经细胞分化及成熟。结果:①Morris水迷宫实验显示,与对照组相比,AD组逃避潜伏期显著延长（P<0.05）;AD+有氧训练组逃避潜伏期较AD组显著缩短（P<0.05）。②与对照组比,AD组齿状回区Hoechst阳性细胞显著增多（P<0.05）;AD+有氧训练组Hoechst阳性细胞较AD组显著减少（P<0.05）。③与对照组比,AD组齿状回Brdu、Brdu/NeuN双染阳性细胞明显减少（P<0.05）;AD+有氧训练组较AD组相比齿状回Brdu、Brdu/NeuN双染阳性细胞明显增多（P<0.05）。结论:有氧训练后,AD大鼠海马亚颗粒细胞区神经细胞的凋亡减少,齿状回神经再生增加,上述改变可能为有氧训练改善AD大鼠认知行为能力的机制之一。     

Wake-promoting effects of vagus nerve stimulation after traumatic brain injury: upregulation of orexin-A and orexin receptor type 1 expression in the prefrontal cortex

Orexins, produced in the lateral hypothalamus, are important neuropeptides that participate in the sleep/wake cycle, and their expression coincides with the projection area of the vagus nerve in the brain. Vagus nerve stimulation has been shown to decrease the amounts of daytime sleep and rapid eye movement in epilepsy patients with traumatic brain injury. In the present study, we investigated whether vagus nerve stimulation promotes wakefulness and affects orexin expression. A rat model of traumatic brain injury was established using the free fall drop method. In the stimulated group, rats with traumatic brain injury received vagus nerve stimulation(frequency, 30 Hz; current, 1.0 mA; pulse width, 0.5 ms; total stimulation time, 15 minutes). In the antagonist group, rats with traumatic brain injury were intracerebroventricularly injected with the orexin receptor type 1(OX1R) antagonist SB334867 and received vagus nerve stimulation. Changes in consciousness were observed after stimulation in each group. Enzyme-linked immunosorbent assay, western blot assay and immunohistochemistry were used to assess the levels of orexin-A and OX1R expression in the prefrontal cortex. In the stimulated group, consciousness was substantially improved, orexin-A protein expression gradually increased within 24 hours after injury and OX1R expression reached a peak at 12 hours, compared with rats subjected to traumatic brain injury only. In the antagonist group, the wake-promoting effect of vagus nerve stimulation was diminished, and orexin-A and OX1 R expression were decreased, compared with that of the stimulated group. Taken together, our findings suggest that vagus nerve stimulation promotes the recovery of consciousness in comatose rats after traumatic brain injury. The upregulation of orexin-A and OX1R expression in the prefrontal cortex might be involved in the wake-promoting effects of vagus nerve stimulation.     

Functional inactivation of orexin 1 receptors in CA1 region impairs acquisition, consolidation and retrieval in Morris water maze task

Orexin containing neurons in the lateral hypothalamic area (LHA) produce orexin-A (hypocretin-1) and orexin-B (hypocretin-2) and send their axons to the hippocampus, which predominantly expresses orexin 1 receptors (OX1Rs) showing a higher affinity to orexin-A. Recent studies have shown that central administration of orexin-A has an effect on learning and memory but literature concerning the role of orexinergic system in cognition remains controversial. Therefore, we examined the effect of pre-training, post-training and pre-probe trial intrahippocampal CA1 administration of a selective OX1R the orexin 1 receptor antagonist SB-334867-A (1.5, 3, 6 microg/0.5 microl) on acquisition, consolidation and retrieval in a single-day testing version of Morris water maze (MWM) task. Our results show that, SB-334867-A impaired acquisition, consolidation and retrieval of MWM task as compared with the control group. This drug had no effect on escape latency of a non-spatial visual discrimination task. Therefore, it seems that endogenous orexins, especially orexin-A, play an important role in spatial learning and memory in the rat.     

慢性强迫游泳应激对大鼠海马神经元再生和p-CREB表达的影响

目的 研究慢性强迫游泳应激模型大鼠海马神经元再生和磷酸化环磷酸腺苷反应元件结合蛋白（p-CREB）的表达.方法 30只雄性SD大鼠随机分为3组：强迫游泳7 d组（S1组）、强迫游泳14 d组（S2组）和对照组.S1组和S2组分别连续强迫游泳7 d和14 d,每天5 min,水温（10±0.5）℃.采用免疫组化半定量测定大鼠海马5-溴脱氧尿苷（BrdU）和p-CREB阳性细胞表达情况.结果 免疫组化结果 显示,在整个海马结构中BrdU及p-CREB的阳性细胞主要集中于齿状回的颗粒细胞下层.与对照组比较,S1组、S2组大鼠海马齿状回BrdU和p-CREB阳性细胞数均明显减少（P＜0.01）;而与S1组比较,BrdU阳性细胞数无统计学差异（P＞0.05）,S2组p-CREB阳性细胞数进一步减少（P＜0.01）.结论 慢性强迫游泳应激可导致海马神经元再生功能障碍,其机制可能与p-CREB信号转导通路有关. 基金项目：     

Role of orexin receptors in the ventral tegmental area on acquisition and expression of morphine-induced conditioned place preference in the rats

The orexins are hypothalamic neuropeptides and their role in reward processing and drug addiction has been demonstrated. The extent of involvement of each orexin receptor in the acquisition and expression of conditioned place preference (CPP) for morphine is still a matter of controversy. We investigated the functional differences between orexin-1 and -2 receptor blockade in the ventral tegmental area (VTA) on the acquisition and expression of morphine CPP. A total of 86 adult male Wistar rats weighing 250 ± 30 g (age 7–8 weeks) received intra-VTA microinjection of either SB334867 (0.1, 1 and 10 nM), a selective orexin-1 receptor (OX1R) antagonist, or TCS-OX2-29 (1, 5 and 25 nM), a selective orexin-2 receptor (OX2R) antagonist. To measure the acquisition, the animals received each antagonist (SB334867 or TCS-OX2-29) 5 min prior to subcutaneous injection of morphine (5 mg/kg) during the conditioning phase. To measure the CPP expression, the animals received each antagonist on the post-conditioning phase. The CPP conditioning score was recorded by Ethovision software. Data showed that intra-VTA microinjection of OX1-R antagonist significantly attenuated morphine CPP acquisition, during the conditioning phase, and expression, during the post-conditioning phase. Intra-VTA microinjection of OX2-R antagonist also significantly attenuated morphine CPP acquisition and expression in the mentioned phases. Our results showed the orexin role in learning and memory and indicate that orexin receptors (OX1R and OX2R) function in the VTA is essential for both acquisition and expression of morphine reward in rats in the CPP model.