Mechanisms of comorbidity between epilepsy and depression

描述(由申请人提供)：该项目的长期目标是了解癫痫和抑郁症共同发病的机制。目前的建议验证了癫痫相关抑郁可能源于中枢去甲肾上腺素能传递的特定功能障碍的假说。这项研究的重点是上行去甲肾上腺素途径和调节去甲肾上腺素(NE)释放的肾上腺素受体的可塑性。这项研究采用了一种动物模型，在匹罗卡品诱导的癫痫持续状态后，Wistar大鼠出现慢性癫痫和并发的抑郁样损害。研究的第一部分描述了中枢去甲肾上腺素能传递的扰动与抑郁行为损害的严重程度有关，后者是通过强迫游泳测试进行测量和分类的。用在体快循环伏安法和酪氨酸羟基酶免疫荧光法测定蓝斑-前脑(即海马区和新皮质)去甲肾上腺素能投射的强度和完整性。用放射自显影和电子显微镜研究调节NE释放的肾上腺素受体(即蓝斑的体树突状自体受体和前脑的轴突自体受体)以及调节前脑的5-羟色胺释放的肾上腺素受体(即异型受体)的数量和功能。这项研究的第二部分考察了在上行通路中恢复去甲肾上腺素能传递是否对患有癫痫相关抑郁的动物起到治疗作用。选择性去甲肾上腺素再摄取抑制剂瑞波西汀将在两周内交付使用。选择性2A型肾上腺素受体阻滞剂RX-821002将局部注射到蓝斑、海马体、新皮质和中缝核内，以靶向特定数量的2A型肾上腺素受体。治疗对抑郁行为的影响，前脑去甲肾上腺素和5-羟色胺的释放，酪氨酸羟基酶的表达，以及2a肾上腺素受体的数量、功能和亚细胞定位将分别使用上述技术进行检测。在这项研究的第三部分，将研究导致中枢去甲肾上腺素能功能障碍的可能上游机制。下丘脑-垂体-肾上腺皮质轴的失调将用放射免疫测定法进行研究，并与去甲肾上腺素能损伤的程度相关；进一步，将检测局部向蓝斑注射糖皮质激素受体阻滞剂米非司酮对中枢去甲肾上腺素能缺陷和抑郁行为的影响。这些研究将有助于我们理解癫痫和抑郁症共病的机制，有助于发展这种疾病的循证治疗，并有助于改善合并抑郁症的癫痫患者的生活质量。

DESCRIPTION (provided by applicant): The long-term objective of the project is to understand mechanisms of co-morbidity between epilepsy and depression. The present proposal tests the hypothesis that epilepsy-associated depression may stem from specific dysfunction of central noradrenergic transmission. The study focuses on the ascending noradrenergic pathway and on the plasticity of ¿2A adrenoreceptors that regulate norepinephrine (NE) release in this pathway. The study employs an animal model whereby chronic epilepsy and concurrent depression-like impairments develop in Wistar rats following pilocarpine-induced status epilepticus. The first part of the study describes perturbations in central noradrenergic transmission in relation to the severity of depressive behavioral impairments, the latter being measured and classified using the forced swim test. The strength and the integrity of noradrenergic transmission in the locus coeruleus-forebrain (i.e. the hippocampus and the neocortex) noradrenergic projections will be measured by means of the in vivo fast cyclic voltammetry, as well as the tyrosine hydroxylase immunofluorescence. The number and the function of ¿2A adrenoreceptors that regulate NE release (i.e. somatodendritic autoreceptors in locus coeruleus and axonal autoreceptors in the forebrain), as well those that regulate serotonin release in the forebrain (i.e. heteroreceptors) will be characterized using autoradiography and electron microscopy. The second part of the study examines whether restoring noradrenergic transmission in the ascending pathway exerts therapeutic effects in animals with epilepsy-associated depression. A selective norepinephrine reuptake inhibitor reboxetine will be delivered over two weeks. A selective ¿2A adrenoreceptor blocker RX-821002 will be administered locally into the locus coeruleus, the hippocampus, the neocortex, and in raphe nucleus, in order to target specific population of ¿2A adrenoreceptors. The effects of treatments on depressive behavior, norepinephrine and serotonin release in the forebrain, tyrosine hydroxylase expression, as well as the number, function and subcellular localization of ¿2A adrenoreceptors will be examined using respective techniques listed above. In the third part of the study possible upstream mechanisms leading to central noradrenergic dysfunction will be examined. The dysregulation of the hypothalamo-pituitary-adrenocortical axis will be studied using radioimmunoassay and correlated with the extent of noradrenergic impairments; further the effects of a glucocorticoid receptor blocker mifepristone delivered locally into the locus coeruleus, on central noradrenergic deficits and depressive behavior will be examined. The proposed studies will contribute to our understanding of mechanisms of the comorbidity between epilepsy and depression, to the development of evidence-based therapies of this condition, and to improving of the quality of life in those epilepsy patients who suffer from concurrent depression.