Investigation of the relationship between antinociceptive mechanism of antidepressant and descending noradrenergic inhibitory pathway

迄今为止的研究结果表明，三环类抗抑郁药，如阿米替林，具有抗伤害感受作用。据推测，下行抑制神经元参与抗抑郁药的抗伤害感受作用。下行抑制性神经元，包括去甲肾上腺素能神经元，产生抗伤害感受的机制仍不清楚。最近的电生理研究表明，去甲肾上腺素激活脊髓中的GABA能中间神经元，表明其在介导抗伤害感受效应中的作用。我们研究了阿米替林是否激活脊髓中的GABA能中间神经元，Fos蛋白作为神经元活化的标志物成年雄性Wistar大鼠鞘内施用0（对照）、15、30、60或90 μ g阿米替林。4小时后，通过腹腔内注射戊巴比妥麻醉动物，并用多聚甲醛灌注以进行固定。在腰椎水平和前后方向解剖脊髓， ...更多信息 然后用氯苄氨基青霉素对切好的切片进行c-Fos蛋白染色，并计数c-Fos阳性细胞的数目。还用荧光偶联的第二抗体对切片进行c-Fos和谷氨酸脱羧酶（GAD ; GABA合成的限速酶）的双重染色。在接下来的研究中，给大鼠注射哌唑嗪（α 1肾上腺素受体拮抗剂）或育亨宾（α 2肾上腺素受体拮抗剂）鞘内注射，15 min后鞘内注射阿米替林60 μg，脊髓背角c-Fos阳性细胞数呈剂量依赖性增加，平均每片40.8个。90 μg组为89.2。阿米替林诱导的c-Fos蛋白表达定位于I、II、III和IV层。通过双重染色分析表明，约80%的c-Fos阳性细胞与GAD阳性细胞共定位。阿米替林诱导的c-Fos可被哌唑嗪阻断，但育亨宾不阻断。本研究结果表明阿米替林通过α 1肾上腺素受体激活脊髓背角GABA能中间神经元。我们的研究结果表明，GABA能中间神经元和它们的下游效应器至少在脊髓中阿米替林的抗伤害作用中起作用。少

Findings to date indicate that tricyclic antidepressants, such as amitriptyline, have an antinociceptive effect It is supposed that descending inhibitory neurons are involved in the antinociceptive action of antidepressants. The mechanism whereby descending inhibitory neurons, including noradrenergic neurons, produce antinociception remains unclear Recent electrophysiological studies have shown that noradrenalin activates GABAergic interneurons in the spinal cord, suggesting its role in mediating the antinociceptive effect In the present study, we investigated whether amitriptyline activates GABAergic interneurons in the spinal cord using c-Fos protein as a marker for neuronal activation.Adult male Wistar rats were administered 0 (control), 15, 30, 60 or 90 pg of amitriptyline intrathecally. After 4 hours, animals were anesthetized with intraperitoneal injection of pentobarbital and perfused with paraformaldehyde for fixation. The spinal cords were dissected at the lumbar level and fro … More zen-sectioned Sections were then stained for c-Fos protein using cliaminobenzicline and the number of c-Fos positive cells was counted Sections also double stained for c-Fos and glutamic acid decarboxylase (GAD ; a rate-limiting enzyme for GABA synthesis) using fluorescent conjugated secondary antibodies. In the following study, rats were injected with prazosin (alpha 1 adrenoceptor antagonist) or yohimbine (alpha 2 adrenoceptor antagonist) intrathecally and, 15 min later were injected 60 μg of amitriptyline intrathecally.Amitriptyline administration increased c-Fos positive cells in the dorsal horn of the spinal cord in a dose-dependent manner The number of c-Fos positive cells per section was 40.8 (mean) in control group, while 89.2 in 90 μg group. Amitriptyline-induced c-Fos protein expression was localized within the laminae I, II, III and IV Analysis by double staining indicated that approximately 80% of c-Fos positive cells were colocalized with GAD positive cells. Amitriptyline-induced c-Fos was blocked by prazosin but not by yohimbine.Results from the present study indicate that amitriptyline activates GABAergic interneurons through alpha 1 adrenoceptor in the dorsal horn of the spinal cord. Our finding suggests that GABAergic interneurons and their downstream effectors play at least a part in the antinociceptive action of amitriptyline in the spinal cord. Less