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发病的机制。本研究验证了癫痫相关性抑郁可能源于中枢去甲肾上腺素能传导特异性功能障碍的假说。本研究的重点是上行去甲肾上腺素能通路，以及在该通路中调节去甲肾上腺素（NE）释放的¿2A肾上腺素受体的可塑性。该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抑郁样损伤。研究的第一部分描述了与抑郁症行为障碍严重程度相关的中枢性去肾上腺素能传递的扰动，后者使用强迫游泳测试进行测量和分类。通过体内快速循环伏安法和酪氨酸羟化酶免疫荧光法测定蓝斑-前脑（即海马和新皮层）去甲肾上腺素能投射的强度和完整性。调节NE释放的¿2A肾上腺受体（即蓝斑体突自受体和前脑轴突自受体）的数量和功能，以及调节前脑血清素释放的肾上腺受体（即异受体）将使用放射自显影和电子显微镜进行表征。本研究的第二部分探讨了恢复上升通路的去甲肾上腺素能传递是否对癫痫相关性抑郁症动物产生治疗作用。选择性去甲肾上腺素再摄取抑制剂瑞波西汀将在两周内给药。选择性¿2A肾上腺素受体阻滞剂RX-821002将局部应用于蓝斑、海马、新皮质和中缝核，以靶向特定的¿2A肾上腺素受体群体。治疗对抑郁行为、前脑去甲肾上腺素和血清素释放、酪氨酸羟化酶表达以及¿2A肾上腺素受体的数量、功能和亚细胞定位的影响将使用上述各自的技术进行检查。在研究的第三部分，可能的上游机制导致中枢去肾上腺素能功能障碍将被检查。下丘脑-垂体-肾上腺皮质轴的失调将使用放射免疫法进行研究，并与去甲肾上腺素能损伤的程度相关；此外，糖皮质激素受体阻滞剂米非司酮局部递送到蓝斑，对中枢性去肾上腺素能缺陷和抑郁行为的影响将被检查。这些研究将有助于我们理解癫痫和抑郁共病的机制，有助于开发基于证据的治疗方法，并有助于改善癫痫并发抑郁症患者的生活质量。

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.