Anandamide對大鼠喉返神經外展支與內收支活性影響之研究

Responses of the Abducent and Adducent Branches of the Recurrent Laryngeal Nerve to Anandamide Administration in the Rat

蔡緻怡(Chih-Yi Tsai)

指導教授 ： 黃基礎

國立臺灣師範大學/理學院/生命科學研究所/碩士(2006年)

摘要

聲門運動端靠喉頭內收肌與外展肌調控。這兩群肌肉分別由喉返神經內收支與外展支支配，內收支具有呼氣活性，使內收肌在呼氣時收縮而縮小聲門面積；外展支於吸氣時期放電，活動時使外展肌收縮而擴大聲門孔徑。本實驗室最近的研究發現，辣椒素刺激肺迷走C纖維後會興奮喉返神經內收支與抑制外展支的活性並誘發聲門關閉。辣椒素為transient receptor potential vanilloid type 1 ( TRPV1 receptor) 的外生性致效劑，而與其結構相似的內生性脂質代謝物anandamide是否會經由活化肺迷走C纖維而改變上呼吸道的暢通至今還沒有相關的研究。Anandamide為一內生性的cannabinoid，已被證實可經由活化TRPV1接受器而興奮肺迷走C纖維，因此本研究擬探討TRPV1的內生性致效劑anandamide是否會影響喉返神經活性來調控喉頭的暢通。本實驗以雄性Wistar品系大白鼠為實驗動物並以urethane (1.2 g/kg) 腹腔麻醉，接著進行氣管插管、股動、靜脈插管，及頸靜脈插管。頸靜脈插管通向右心房，使注射的anandamide能進入肺循環興奮肺迷走C纖維。接著以gallamine thriethiodide (5 mg/kg，靜脈注射) 麻痺肌肉，接上人工呼吸器提供動物純氧。分離膈神經、喉返神經內收支及外展支並測量其活性。本實驗分為三部分，首先觀察不同劑量的anandamide (0.25、0.5及1 mg/kg) 是否會影響喉返神經內收支與外展支的活性。再者，因anandamide同時也是大麻鹼 (CB) 接受器的致效劑，因此第二部分實驗利用TRPV1與CB1接受器的拮抗劑來釐清anandamide影響喉返神經活性的作用是經由活化哪一類受器而產生。最後，利用數位相機拍攝聲門運動，觀察頸靜脈注射anandamide是否會改變自發性呼吸大鼠的聲門運動。實驗結果發現，中 (0.5 mg/kg) 與高劑量 (1 mg/kg) 的anandamide皆會引起肺化學反射，其特徵為呼吸暫停、降壓及抑心反應。此外，anandamide還會興奮喉返神經內收支並抑制外展支的活性，且使內收支由呼氣活動提前在吸氣時開始放電，外展支則由原本提前於膈神經前放電變為延遲。這些反應皆可被TRPV1拮抗劑 (capsazepine) 阻斷，但不受CB1拮抗劑 (AM281) 影響。第三部份結果顯示anandamide還可使聲門在呼吸暫停以及恢復期間緊緊關閉。這些結果顯示，anandamide可能是經由活化TRPV1接受器，引起反射作用來影響喉返神經內收支與外展支的活性，並進一步引起聲門關閉，同時也暗示著內生性的anandamide可能在病理情況之下經由興奮肺迷走C纖維來調控上呼吸道的暢通。

關鍵字

喉返神經 ； anandamide ； 肺迷走C纖維受器 ； TRPV1

並列摘要

Vocal fold movement is modulated by the coordination of the laryngeal abducent muscles (abductor) and adducent muscles (adductor) during respiratory cycle. Contraction of the abductor which is supplied by the abducent branch of the recurrent laryngeal nerve (Abd RLN) widens the glottal aperture during inspiration, while contraction of the adductor which is innervated by the adducent branch of the RLN (Add RLN) narrows the glottis during expiration. Previous studies in our lab have shown that capsaicin-induced activation of pulmonary vagal C-fiber (PCF) receptors reflexively excites the Add RLN activity but inhibits the Abd RLN discharge, suggesting that the glottis is closed. It is not clear whether anandamide (AEA), an endogenous agonist of transient receptor potential vaniloid-1 (TRPV1, also called capsaicin receptor), might also elicit a similar reflex effect on the RLN as was induced by capsaicin. Aim of the present study was therefore to investigate whether AEA administration could produce a modulation of the glottal patency through activation of PCF receptors. Male Wistar rats were treated with atropine (0.5 mg/kg, i.p.) and then anesthetized with urethane (1.2 g/kg, i.p.). Catheterization of the femoral artery and vein, and jugular vein was performed for measuring blood pressure (BP) and drug administration, respectively. The animal was paralyzed and ventilated. Fractional concentration of carbon dioxide (FETCO2) was maintained at normocapnia in hyperoxia. In the first protocol, activities of the phrenic nerve (PNA), Add RLN (Add RLNA), and Abd RLN (Add RLNA) were examined in response to varied doses of AEA (0.25, 0.5 and 1 mg/kg). The present results showed that AEA administration evoked cardiopulmonary chemoreflex, characterized by apnea, hypotension, and bradycardia. An enhancement of Add RLNA during apneic period and recovery from apnea, reflecting an increase in amplitude and earlier onset during inspiration was dicerned. Concomitantly, a delay onset and decrease of Abd RLN discharge was observed. In the second protocol, pretreatment of TRPV1 antagonist capsazepine (CZP, 4.5 mg/kg) and CB1 antagonist AM281 (0.3 mg/kg) was performed to elucidate which one of these two receptors might be involved in AEA-induced changes in laryngeal functions. The RLN responses to AEA administration were abolished by pretreatment with capsazepine but not with AM 281. Finally, vocal fold movement was monitored using a digital camera under microscope in spontaneously breathing rats with simultaneously recording of diaphragmatic EMG activity. The observed results revealed that a tightly glottal closure was occurred during anandamide-induced apnea. These results suggest that anandamide-induced glottal closure is probably mediated through activation of TRPV1 on the PCF to produce a reflex modulation of the RLN activity.

並列關鍵字

recurrent laryngeal nerve ； anandamide ； pulmonary vagal C-fiber ； TRPV1

參考文獻

109. 蔡緻怡、吳季瑾、李昆澤、黃基礎。M2蕈鹼接受器參與辣椒素引起大鼠抑心與降壓作用。BioFormosa 40:25-35，2005。

1. Adachi T, Umezaki T, Matsuse T, Shin T. Changes in laryngeal muscle activities during hypercapnia in the cat. Otolaryngol Head Neck Surg 118:537-544, 1998.

2. Agostoni E, Chinnock JE, Daly M de B, Murray JG. Functional and histological studies of the vagus nerve and its branches to the heart, lungs and abdominal viscera in the cat. J Physiol 135:182-205, 1957.

3. Balis UJ, Morris KF, Koleski J, Lindsey BG. Simulations of a ventrolateral medullary neural network for respiratory rhythmogenesis inferred from spike train cross-correlation. Biol Cybern 70:311-327, 1994.

4. Barillot JC, Grelot L, Reddad S, Bianchi AL. Discharge patterns of laryngeal motoneurones in the cat: an intracellular study. Brain Res 509:99-106, 1990.