Laorden M Luisa, Núñez Cristina, Almela Pilar, Milanés M Victoria
Equip of Cellular and Molecular Pharmacology, University School of Medicine, Campus de Espinardo, 30100 Murcia, Spain.
J Neurochem. 2002 Oct;83(1):132-40. doi: 10.1046/j.1471-4159.2002.01123.x.
We previously demonstrated that morphine withdrawal induced hyperactivity of noradrenergic pathways innervating the hypothalamic paraventricular nucleus (PVN) in rats, in parallel with an increase in the neurosecretory activity of the hypothalamus-pituitary-adrenocortical (HPA) axis, as evaluated by corticosterone release. These neuroendocrine effects were dependent on stimulation of alpha-adrenoceptors. In the present study, Fos immunostaining was used as a reflection of neuronal activity and combined with immunostaining for tyrosine hydroxylase (TH) for immunohistochemical identification of active neurones during morphine withdrawal. Dependence on morphine was induced by 7-day chronic subcutaneous implantation of six morphine pellets (75 mg). Morphine withdrawal was precipitated by administration of naloxone (5 mg/kg subcutaneously) on day 8. Fos immunoreactivity in the PVN and also in the nucleus tractus solitarius (NTS)-A2 and ventrolateral medulla (VLM)-A1 cell groups, which project to the PVN, increased during morphine withdrawal. Following withdrawal, Fos immunoreactivity was present in most of the TH-positive neurones of the A2 and A1 neurones. In a second study, the effects of administration of adrenoceptor antagonists on withdrawal-induced Fos expression in the PVN were studied. Pre-treatment with alpha1- or alpha2-adrenoceptor antagonists, prazosin (1 mg/kg intraperitoneally) and yohimbine (1 mg/kg intraperitoneally), respectively, 20 min before naloxone administration to morphine-dependent rats markedly reduced Fos expression in the PVN. Similarly, pre-treatment with the beta antagonist, propranolol (3 mg/kg intraperitoneally), significantly prevented withdrawal-induced Fos expression. Collectively, these results suggest the hypothesis that noradrenergic neurones in the brainstem innervating the PVN are active during morphine withdrawal, and that activation of transcriptional responses mediated by Fos in the HPA axis following withdrawal are dependent upon hypothalamic alpha- and beta-adrenoceptors.
我们先前证明，吗啡戒断可诱导大鼠中支配下丘脑室旁核（PVN）的去甲肾上腺素能通路的活动亢进，同时下丘脑-垂体-肾上腺皮质（HPA）轴的神经分泌活动增加，这通过皮质酮释放来评估。这些神经内分泌效应依赖于α-肾上腺素能受体的刺激。在本研究中，Fos免疫染色被用作神经元活动的反映，并与酪氨酸羟化酶（TH）免疫染色相结合，用于免疫组织化学鉴定吗啡戒断期间的活性神经元。通过7天慢性皮下植入6个吗啡丸（75毫克）诱导对吗啡的依赖性。在第8天通过皮下注射纳洛酮（5毫克/千克）引发吗啡戒断。在吗啡戒断期间，PVN以及投射到PVN的孤束核（NTS）-A2和延髓腹外侧（VLM）-A1细胞群中的Fos免疫反应性增加。戒断后，A2和A1神经元的大多数TH阳性神经元中存在Fos免疫反应性。在第二项研究中，研究了肾上腺素能受体拮抗剂给药对戒断诱导的PVN中Fos表达的影响。在给吗啡依赖大鼠注射纳洛酮前20分钟，分别用α1-或α2-肾上腺素能受体拮抗剂哌唑嗪（1毫克/千克腹腔注射）和育亨宾（1毫克/千克腹腔注射）进行预处理，可显著降低PVN中的Fos表达。同样，用β拮抗剂普萘洛尔（3毫克/千克腹腔注射）进行预处理可显著阻止戒断诱导的Fos表达。总体而言，这些结果提出了一个假设，即支配PVN的脑干中的去甲肾上腺素能神经元在吗啡戒断期间是活跃的，并且戒断后HPA轴中由Fos介导的转录反应的激活依赖于下丘脑α-和β-肾上腺素能受体。
