Alpha2肾上腺素受体异常表达和激活致喉源性窒息的中枢机制及在阻塞性睡眠呼吸暂停发生中的作用

Abnormal nervous control of the larynx and pharynx plays important roles in the pathogenesis of obstructive sleep apnea-hypopnea syndrome (OSAHS). Severe OSAHS is accompanied not only by inspiratory collapse but also by expiratory closure of the upper airway. It has been reported that activation of central alpha2-adrenoceptors results in intermittent expiratory closure of the glottis. This process may be involved in the pathogenesis of OSAHS, but the central mechanisms are unknown. In this project, preganglionic recurrent laryngeal motoneurons (PRLMs) are to be retrogradely labeled and studied in vitro with patch-clamp, in rhythmically active medullary and pon-medullary preparations, respectively. We aim to prove that activation of pontine and/or medullary alpha2-adrenoceptors can selectively excite expiratory PRLMs that innervate the adductor muscles of the glottis. Alpha2A-adrenoceptors (a2A-AR) are to be overexpressed in the pontine noradrenergic nuclei and the medullary PRLM-containing area, and the respiratory behavior during wakeness and sleep is to be monitored with plethysmography. OSAHS rat model is to be established by chronic intermittent hypoxia; and the expression of a2A-AR in the pontine noradrenergic nuclei and in the medullary PRLM-containing area is to be examined using immunohistochemistry. We aim to prove that overexpression and activation of alpha2-adrenoceptors in the pontine noradrenergic nuclei and the medullary PRLM-containing area contribute to the pathogenesis of OSAHS, via causing intermittent closure of the glottis and the resultant hypoxia.

咽喉部神经调控异常在阻塞性睡眠呼吸暂停-低通气综合征(OSAHS)发生中起重要作用.OSAHS不仅有吸气相上气道塌陷,严重时还有呼气相上气道闭塞.资料表明:中枢a2肾上腺素受体(a2-AR)激活可致间歇性呼气相声门关闭,产生呼气性窒息.该作用可能参与OSAHS发生,但中枢机制不明.本项目用逆行追踪法标记大鼠喉返神经节前神经元(PRLM);在具有呼吸节律的延髓脑片及脑桥-延髓标本,用膜片钳记录PRLM,以证明脑桥或延髓内a2-AR激活可选择性地在呼气相兴奋支配声门内收肌的呼气性PRLM.在大鼠脑桥去甲肾上腺素能神经核和/或延髓PRLM区域过表达a2A肾上腺素受体(a2A-AR),观察清醒和睡眠时呼吸节律;建立慢性间歇性缺氧型OSAHS模型大鼠,用免疫组织化学法观察脑桥和/或PRLM区a2A-AR表达,以证明脑桥和/或PRLM区a2-AR高表达或激活可致间歇性声门关闭和缺氧,进而参与OSAHS

咽喉部神经调控异常在阻塞性睡眠呼吸暂停-低通气综合征(OSAHS)发生中起重要作用。OSAHS严重时不仅有吸气相上气道塌陷，还有呼气相上气道闭塞。资料表明:中枢a2肾上腺素受体(a2-AR)激活可致间歇性呼气相声门关闭,产生呼气性窒息.该作用可能参与OSAHS 发生,但中枢机制不明.本项目用逆行追踪法标记新生大鼠喉返神经节前神经元(PRLMs)；在具有呼吸节律的延髓脑片,用膜片钳记录PRLMs.在10日龄幼年大鼠用肺功能仪测定气道功能.以图证明延髓内a2-AR激活可选择性地在呼气相兴奋支配声门内收肌的呼气性(吸气抑制性)PRLMs。发现：.PRLMs有吸气激活型(inspiratory-activated PRLMs, IA-PRLMs)和吸气抑制型(inspiratory-inhibited PRLMs, II-PRLMs)。IA-PRLMs主要接受GABA能抑制性突触传入,电压钳下表现为吸气相抑制性突触电流减少或消失，电流钳下呈持续性动作电位发放;II-PRLMs同时接受GABA能和甘氨酸能抑制性突触传入,电压钳下表现为吸气相抑制性突触电流增多,电流钳下表现为吸气相超级化.右旋美托咪啶（Dexmedetomidine，Dex-Med）是一种高选择性的a2-AR激动剂,它在1 uM无显著作用,但在10 M则显著抑制两类PRLMs的GABA能和甘氨酸能IPSCs的频率和幅度,并使舌下神经根放电频率和强度进行性下降.Dex-Med的上述效应不能被选择性的a2-AR阻断剂SKF-86466所阻断,但能够被a2-AR和咪唑啉受体的混合阻断剂efaroxan所阻断.10 uM Dex-Med对两类PRLMs的静息电位以及谷氨酸能突触传入均无显著影响.在幼年大鼠,经小脑延髓池微注射低剂量（1 mM, 5 uL）及高剂量（5 mM, 5 uL）Dex-Med均可持续显著地抑制动物的呼吸频率,但对潮气量无明显影响.这种效应不能被SKF-86466阻断,但可被Efaroxan部分甚至完全阻断.以上结果提示:Dex-Med同时作用于a2-AR和咪唑啉受体,并通过这些机制导致呼吸节律中枢抑制以及PRLMs"去抑制".这些机制可能与中枢性和阻塞性呼吸暂停发生有关.临床发现Dex-Med等a2-AR激动剂无明显呼吸抑制效应,但本研究部支持这一结论.