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  • 學位論文

急性肛門擴張經由GABA神經傳導抑制麻醉老鼠在NMDA依賴性的骨盆-尿道反射增益現象

Acute Anal Stretch Inhibits NMDA-Dependent Pelvic-Urethra Reflex Potentiation via Spinal GABAergic Inhibition in Anesthetized Rats

指導教授 : 林則彬

摘要


肛門擴張在前人的研究中,可以有效降低尿道外括約肌的張力,在脊髓損傷合併逼尿肌外括約肌共濟失調患者是為一有效排尿輔助技術,在我們以肛門擴張器模擬人的手指進行肛門擴張研究,結果顯示,肛門擴張可以明顯降低尿道外括約肌的肌電圖活性,降低百分比達33%。可是在正常人肛門擴張是否也一樣能抑制尿道外括約肌之活性呢?因此本研究為第一個將肛門擴張應用於脊髓完好生物體之實驗。 本實驗的目的在研究肛門擴張,對於在使用 urethane 麻醉的老鼠中對骨盆傳入神經纖維與尿道之間的反射增異現象(reflex potentiation)的影響。 反覆刺激(Repetitive stimulation, RS, 頻率 1 赫茲) 會在骨盆—尿道反射(pelvic-urethral reflex ,PUR)誘發一個增益現象我們稱為脊髓反射增益(spinal reflex potentiation ,SRP) (在控制組及反覆刺激組中,每次刺激所引起的動作電位數目分別為 0.9 ± 0.3 次及 19.4 ± 1.4 次,P 值小於零點零一, N 值為 10)。經由mosquito鉗在麻醉小鼠肛門口依鉗子張開距離做橫向擴張,然後觀察此橫向擴張對於反覆刺激產生脊髓反射增益之影響;當鉗子將肛門口擴張 0.4 厘米時脊髓反射增異(SRP) 並無有意義減少(在控制組及擴張組中,每次刺激所引起的動作電位數目分別為 19.4 ± 1.4 次及 18.4 ± 1.5 次,P 值大於零點零一), 當鉗子將肛門口擴張 0.8 厘米時脊髓反射增益(SRP) 產生有意義減少(在控制組及擴張組中,每次刺激所引起的動作電位數目分別為 19.4 ± 1.4 次及 10.4 ± 1.2 次,P 值小於零點零一)而將擴張程度至1.2厘米時可見反覆刺激所引起之動作電位數目幾乎完全被抑制(19.4 ± 1.4 次及 1.6 ± 0.5 次,P 值小於零點零一) 。且此抑制可部份被椎管內注射 N-methyl-D-aspartic acid (NMDA,100 微莫 耳,10 微升,一次注射) 所逆轉(1.6 ± 0.5 次及 12.4 ± 1.1 次,P 值小於零點零一)。事先經椎管內注射γ-Aminobutyric acid (GABA) A 受體拮抗劑 bicuculline (100 微莫 耳,10 微升,一次注射) 則肛門口擴張所引起之SRP 抑制現象被部份抵銷 (1.6 ± 0.5 次及 11.6± 1.3 次,P 值小於零點零一),但是γ-Aminobutyric acid (GABA) B 受體拮抗劑 hydroxysaclofen (100 微莫 耳,10 微升,一次注射) 則無此效用,因此我們推論肛門擴張能影響尿道外括約肌的活性,且所經之神經傳導路徑及因子至少有部份和γ-Aminobutyric acid (GABA) 有關,雖然在本實驗中只有biculline 才能抵消肛門擴張對SRP 之影響,但是因為 hydroxysaclofen 本身是一較弱之 GABAB 受體拮抗劑 ,且有文獻指出Hydroxysaclofen 也有部份 GABA 致效劑 (agonist)之效用,要確實釐清 GABA 與肛門擴張之關係將是下一步研究之重要課題。

並列摘要


The impact of acute anal stretch on the pelvic-urethra reflex potentiation was examined in urethane-anesthetized rats by recording the external urethra sphincter electromyogram (EUSE) activity evoked by the pelvic afferent stimulation. Test stimulation (TS, 1 stimulation/30 sec) evoked a baseline reflex activity with a single action potential that was abolished by gallamine (5 mg/kg, i.v.). On the other hand, the repetitive stimulation (RS, 1 stimulation/1 sec) induced spinal reflex potentiation (SRP) that was attenuated by intrathecal CNQX (a glutamatergic AMPA receptor antagonist, 100 μM, 10 μl) and APV (a glutamatergic NMDA antagonist, 100 μM, 10 μl). Acute anal stretch using a mosquito clamp with a distance of 4 mm exhibited no effect, while with distances of 8 mm attenuated and of 12 mm abolished the repetitive stimulation-induced SRP. Intrathecal NMDA (100 μM, 10 μl) reversed the abolition on SRP caused by anal stretch. On the other hand, pretreated bicuculline (GABA A receptor antagonist, 100 μM, 10 μl) but not hydroxysaclofen (GABA B receptor antagonist) counteracted the abolition on the repetitive stimulation-induced SRP caused by the anal stretch. All the results suggested that anal stretch may be used as an adjunct to assist voiding dysfunction in patients with overactive urethra sphincter, and that GABAergic neurotransmission is important in the neural mechanisms underlying external urethra sphincter activity inhibited by anal stretch.

參考文獻


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