Effects of morphine on the morphology of the hypocretin and MCH systems

描述（由申请人提供）： 下丘脑泌素（Hcrt，也称为食欲素）神经元与嗜睡症的病理基础有关。我们发现，人类发作性睡病患者平均有90%的Hcrt细胞损失。虽然大多数工作的重点是Hcrt的唤醒功能及其与食物摄入的关系，但我们最近的工作表明，这些细胞的活动不仅仅与唤醒，食物摄入或“不劳而获”的奖励有关。相反，它与奖励“工作”期间的积极情绪和唤醒特别相关（进展报告）。Hcrt神经元对多巴胺神经元有重要的投射，似乎与多巴胺在奖赏中的作用有相同之处，或许还起到了中介作用。长期以来，轶事数据表明，Hcrt缺陷的人类发作性睡病患者对药物成瘾具有抗性。这一发现已经在动物研究中得到了证实。Hcrt和MCH（黑色素浓缩激素）神经元是混合的，似乎在整个睡眠-觉醒周期中具有相互的放电特征。 我们在正常人中看到的Hcrt细胞数量范围为51，000 - 83，000，基于我们已经计数的15个正常大脑。然而，我们最近接受了一个含有114，000个Hcrt细胞的“正常”大脑，比对照组中Hcrt细胞的最高数量（83，000）高37%，比平均数量（76，000）高50%。我们还发现，在这个人的Hcrt神经元的大小显着小于对照组。进一步的调查显示，这个人是一个前海洛因成瘾者，在他死前超过10年没有服用成瘾药物。这表明阿片类药物管理可能会改变Hcrt系统，这种改变可能与前成瘾者经历的渴望有关。在这个提议的初步研究中，我们发现在连续给予吗啡3天后处死的小鼠中的Hcrt细胞具有正常数量，但神经元体积减少，形态改变。这不是一个微妙的影响。吗啡给药仅3天后，面积平均收缩23%。此外，当我们给予吗啡7天和14天时，我们看到Hcrt细胞数量大幅增加。这种变化在Hcrt神经元中从未报道过。在同一项研究中，我们发现吗啡给药大大减少了可识别的MCH细胞的数量，这是一个以前与成瘾无关的细胞群。与Hcrt细胞相比，MCH细胞的大小和形态正常。目前的建议的目标是确定的性质和时间过程中产生的Hcrt和MCH细胞的形态变化，短期吗啡给药，吗啡成瘾和吗啡戒断。我们假设其中一些变化是不可逆转的。我们将研究这些解剖学变化的行为相关性。这些可能包括积极与消极强化任务的表现的改变以及睡眠的改变。我们将获得更多的人类成瘾者大脑，以复制我们最初观察到的Hcrt细胞数量增加。在这项“主要研究证据”中确定Hcrt细胞的特性可以改变，这不仅可能导致对药物成瘾的更好理解，而且还可能导致永久和治疗性改变并可能增强Hcrt功能障碍（包括嗜睡症和抑郁症）的Hcrt功能的技术。

DESCRIPTION (provided by applicant): Hypocretin (Hcrt, also called orexin) neurons have been implicated in the pathology underlying narcolepsy. We found that human narcoleptics, on average, have a 90% loss of Hcrt cells. Although the focus of most work has been on Hcrt's arousal function and its purported relation to food intake, our recent work has shown that activity of these cells is not simply related to arousal, food intake or "unearned" reward. Rather it is specifically linked to positive emotion and arousal during "work" for rewards (Progress Report). Hcrt neurons have major projections to dopamine neurons and appear to share and perhaps mediate aspects of dopamine's involvement in reward. Anecdotal data has long suggested that Hcrt deficient human narcoleptics are resistant to drug addiction. This finding has now been replicated in animal studies. Hcrt and MCH (melanin concentrating hormone) neurons are intermixed and appear to have reciprocal discharge profiles across the sleep-wake cycle. The number of Hcrt cells that we see in normal humans ranges from 51,000-83,000 based on the 15 normal brains we have counted. However, we recently received a "normal" brain that contained 114,000 Hcrt cells, 37% greater than the highest number of Hcrt cells (83,000) and 50% greater than the mean number (76,000), seen in controls. We also found that the size of Hcrt neurons in this individual was significantly smaller than that of controls. Further investigation revealed that this individual wa a former heroin addict, who had not taken addictive drugs for >10 years before his death. This suggested that opiate administration might alter the Hcrt system and that this alteration might be related to the craving experienced by former addicts. In pilot studies for this proposal, we then found that Hcrt cells in mice sacrificed after a 3 day period of continuous morphine administration were of normal number, but had reduced neuronal volume and altered morphology. This was not a subtle effect. Shrinkage averaged 23% in area after only 3 days of morphine administration. Furthermore, when we administered morphine for 7 and 14 days, we saw a substantial increase in Hcrt cell number. Such changes have never been reported in Hcrt neurons. In the same study, we found that morphine administration greatly decreased the number of identifiable MCH cells, a cell group not previously implicated in addiction. In contrast to Hcrt cells, the size and morphology of MCH cells was normal. The goal of the current proposal is to determine the nature and time course of morphological changes in Hcrt and MCH cells produced by short term morphine administration, by morphine addiction and by morphine withdrawal. We hypothesize that some of these changes are irreversible. We will study the behavioral correlates of these anatomical changes. These might include alterations in performance of positive vs. negatively reinforced tasks and modifications of sleep. We will secure additional human addict brains to replicate our initial observation of Hcrt cell number increase. Establishing that the properties of Hcrt cells can be altered in this "proof of principal study" might not only lead to a better understanding of drug addiction, but also lead to techniques to permanently and therapeutically alter and perhaps augment Hcrt function in disorders with Hcrt dysfunction including narcolepsy and depression.