Effect of electrical stimulation on urethral reflex and micturition during bladder distension in anesthetized rats

骨盆神經－尿道外括約肌 (external urethral sphincter, EUS) 反射是膀胱儲存尿液的重要脊髓反射，當骨盆傳入神經持續接受低頻率的重複性電刺激，發現能引發反射活性產生長時間的增強現象，此為骨盆神經－EUS反射增益效應，於增加尿道阻力及尿液蓄積功能上具有顯著影響力。近來，合谷 (Hoku) 穴位的刺激廣泛被運用於處理自主神經功能障礙相關疾病，有實驗顯示，刺激合谷穴位可經體神經－交感神經反射改善膀胱過動的現象。本研究主要目的 (1) 探討膀胱擴張的機械刺激與規律性膀胱收縮週期 (rhythmic micturition contraction, RMCs) 對骨盆神經－EUS反射增益效應的影響，並探討興奮性神經傳導物質麩氨酸在反射增益效應中所扮演的角色；(2) 探討電刺激合谷穴位對膀胱過度擴張－引發等容積膀胱收縮 (isovolumic bladder contractions, IVCs) 與血壓的影響，同時觀察其在臨床上的應用性。因此，本實驗利用不同體積的生理鹽水，使麻醉鼠的膀胱擴張產生機械刺激，同時給予骨盆傳入神經測試性電刺激 (Test stimulation，TS，1/30 Hz，此頻率無法引發反射增益效應)，觀察骨盆神經－EUS反射活性的變化 (實驗一)；另外以連續灌流生理鹽水的方法引發膀胱產生 RMCs，觀察膀胱內壓的變化與引發骨盆神經－EUS 反射增益效應的關聯性 (實驗二)；實驗三藉由麻醉鼠的尿道導管灌注1.5 倍排尿閾值體積的生理鹽水，促使膀胱擴張並產生規律性的 IVCs，同時於合谷穴進行不同頻率的電針刺激，觀察電針刺激對IVCs 與血壓的影響。 由實驗一的結果發現，當麻醉鼠的膀胱排空 (0 cmH2O) 時，TS引發基礎反射活性；重複性刺激 (repetitive stimulation，RS，1 Hz) 則可誘發骨盆神經－EUS反射增益效應；但在膀胱被生理鹽水擴張的條件下 (6~20 cmH2O)， TS可激發骨盆神經－EUS反射活性產生增益現象，而此效應則被 APV或 NBQX (麩氨酸NMDA 或AMPA 接受器的拮抗劑) 完全或部份抑制；相反地，在膀胱排空狀態下由椎管注射麩氨酸或 NMDA可明顯增加反射活性。由上述結果得知，生理鹽水擴張膀胱的機械性刺激，可以引發骨盆神經－EUS 反射增益效應，而且此增益效應受麩氨酸機制的調控。 實驗二的結果顯示，骨盆神經－EUS反射活性隨著儲尿期 (STOR) 及排尿上升期 (VOID-asc) 膀胱內壓 (intravesical presure，IVP) 的增加而產生增益現象，隨著排尿壓力下降期 (VOID-dec) 而減少。但在排尿收縮剛結束 IVP呈現低壓時，TS仍可引發強直後增益效應 (posttentanic potentiation)，即排尿後反射增益現象 (postvoiding reflex potentiation，PVP)。將TS 誘發之反射活性與 IVP 進行回歸分析發現，PVP呈現最大斜率， STOR的斜率也顯著高於VOID-asc 或 VOID-des (P < 0.01)。CNQX (麩氨酸 AMPA 接受器的拮抗劑) 或APV分別使STOR、VOID-asc、VOID-des以及PVP的回歸線斜率顯著下降或減低到近乎水平的程度 (P < 0.01，n = 10)。由上述結果推論，在生理狀態下，可以激發骨盆神經－EUS反射產生增益效應，而且此反射活性的增加與麩氨酸機制有關。 由實驗三的數據得知，IVCs 經由臟器血管反射 (vesico-vascular reflecx，VVR) 使血壓升高；在合谷穴分別進行低頻率 (low frequency，LF，2 Hz) 或高頻率 (high frequency，HF，20 Hz) 的電針刺激 (electro-acupuncture，Ea)，則引起血壓有持續性 (tonic) 或短暫性 (phasic) 的升壓反應，在 IVCs 產生的同時給予 Ea 刺激，發現 IVCs 的振幅及頻率沒有明顯變化。由上述結果推論，本實驗室進行的電針刺激並未如預期影響膀胱本身的活性，但 Ea (electro-acupuncture) 與 VVR (vesico-vascular reflex) 兩者所引發的升壓反應有加成效應。因此，我們建議在未來臨床應用針灸處理的過程中，應更小心監控病人有無自主功能異常 (autonomic dysfunction) 的病徵或症狀。The pelvic-to-external urethral sphincter (EUS) reflex activity plays an essential role in developing urethral resistance, particularly in the storage phase of micturition cycle. Pelvic nerve-to-EUS reflex potentiation, which may be physiologically relevant in urethra closer mechanism, is characterized by a long-lasting pelvic nerve-to-EUS reflex activity induced by repetitive stimulation (RS, 1 Hz). Recently, acupuncture of the Hoku point was widely employed to treat patients suffering from various autonomic disorders. Researchers investigating the mechanism underlying acupuncture suggested that stimulation at Hoku might ameliorate hyperactive bladder via somato-sympathetic reflexes. The purposes of our present studies are (1) to demonstrate the effect of urinary mechanical stimulation and rhythmic micturition contractions (RMCs) on pelvic nerve-to-EUS reflex potentiation and to clarify the underlying glutamatergic mechanism, (2) to evaluate the effect of electro-acupuncture (Ea) on bladder-distention induced isovolumic bladder contractions (IVCs). Therefore, we tried to find out whether the reflex potentiation would be evoked by test stimulation (TS, 1/30 Hz) on pelvic afferent nerve under two bladder distention models: (1) incremental bladder intravesical pressure (IVP, 0~20 cmH2O) of anesthetized rats was induced by infusion of fixed volume saline into the bladder (experiment I) and (2) RMCs of anesthetized rats was induced by a continuous saline infusion (experiment II). In experiment III, the effect of Ea with different stimulation frequencies on IVCs and blood pressure was studied. In experiment I, the EUS electromyogram activity, evoked by TS or by RS, was recorded with/without bladder saline distension (DIS/non-DIS). TS +non-DIS (0 cmH2O) evoked a single action potential in the reflex activity, whereas RS + non-DIS and TS +DIS (6 20 cmH2O) both elicited a long-lasting reflex potentiation. The TS+DIS -induced reflex potentiation was abolished or attenuated by APV or NBQX (a glutamatergic NMDA or AMPA receptor antagonist). Intrathecal administration of glutamate and NMDA both induced long-lasting reflex potentiation, which was similar to the reflex potentiation observed from TS+DIS. Our findings suggested that saline distension of the rat bladder may elicit a pelvic nerve-to-EUS reflex potentiation and the glutamatergic mechanism may contribute to the presence of such a reflex potentiation. In experiment II, through the intrathecal administration of CNQX (a glutamatergic AMPA receptor antagonist) and APV, TS-evoked reflex activities were demonstrated to potentiate as the IVP of storage phase (STOR) and of ascending period in voiding phase (VOID-asc) increased. In contrary, the TS-evoked reflex activities were reduced as the IVP of descending period in voiding phase (VOID-des) decreased. A TS-evoked postvoiding reflex potentiation (PVP), also characterized as posttetanic potentiation, was observed right after the occurrence of a voiding contraction. Regression analysis of the relationship between evoked activities and IVP revealed that the slope value of the regression line of evoked activities versus the IVP during the STOR was significantly (p<0.01) higher than that of VOID-asc or VOID-des. In addition, the slope of the regression line of PVP was significantly higher than that of the STOR (p<0.01). Intrathecal administration of CNQX or APV significantly decreased the slopes of the STOR, VOID-asc, VOID-des and PVP regression lines (p<0.01, n=10). Our results suggested that a potentiation in the pelvic nerve-to-EUS reflex could be induced under physiological conditions and the glutamatergic mechanism appeared to be involved in this reflex potentiation. In experiment III, the pressor effects on blood pressure (BP) elicited by Ea stimulations and vesico-vascular reflex (VVR) were investigated in an over-distended bladder animal model (1.5 times volume of saline that micturition threshold hold). The Hoku (Li-4) was stimulated by a low frequency Ea (LFEa, 2 Hz) and a high frequency Ea (HFEa, 20 Hz) with intensities 20 times that of the motor threshold. The patterns of pressor effects elicited by an LFEa and an HFEa at Hoku were different, i.e., LFEa at Hoku elicited a tonic pressor effect, while HFEa elicited a phasic one. The VVR induced by IVCs also elicited a pressor effect on BP. Ea stimulation did not modify the amplitudes or frequencies of IVCs, but both of VVR- and Ea-induced pressor responses were superimposed. Our data showed that the bladder function was not significantly affected by Ea stimulation. In addition, the BP pressor effects elicited by the VVR and the Ea stimulation were additive responses. Therefore, monitoring for signs and symptoms of autonomic dysfunction is suggested to patients that received acupuncture treatments.Contents Chinese abstract i Abstract iii List of figures ix List of abbreviations xi Preface 1 1. Neurophysiology of the lower urinary tract 4 2. Role of glutamate play in micturition reflex pathways 7 3. Activity-dependent reflex plasticity 9 4. Electro-acupuncture application 11 5. Objectivs of present study 12 Chapter I Spinal glutamatergic NMDA-dependent pelvic nerve-to-external urethra sphincter reflex potentiation caused by a mechanical stimulation in anesthetized rat 14 1. Abstract 15 2. Introduction 16 3. Materials and methods 19 3-1 Animal preparations 19 3-2 Intrathecal catheter 19 3-3 Intravesical pressure and intraurethral pressure recording 20 3-4 Nerve dissection… 21 3-5 External urethral sphincter electromyogram recording 21 3-6 Experimental protocols 21 3-7 Application of drugs 22 3-8 Data analysis 22 4. Results 24 4-1 Baseline reflex activities. 24 4-2 Repetitive stimulation-induced reflex potentiation. 26 4-3 Saline distension-induced reflex potentiation. 28 4-4 Spinal cord transections.. 30 4-5 Glutamatergic and GABAergic antagonists.... 30 4-6 Effects of glutamatergic agonists.... 31 4-7 Secondary changes resulting from the reflex potentiation.... 34 5. Discussion 36 Chapter II Spinal glutamatergic NMDA-dependent cyclic pelvic nerve-to-external urethra sphincter reflex potentiation in anesthetized rats 42 1. Abstract 43 2. Introduction 45 3. Materials and methods 48 3-1 Animal preparations 48 3-2 Intrathecal catheter 48 3-3 Intravesical pressure recording 49 3-4 External urethral sphincter electromyogram recording 50 3-5 Pelvic nerve stimulation 50 3-6 Application of drugs 52 3-7 Data analysis 52 4 Results 53 4-1 Baseline reflex activities. 53 4-2 Repetitive stimulation-induced reflex potentiation. 55 4-3 Cyclic reflex potentiation. 55 4-4 Postvoiding reflex potentiation.. 61 4-5 Glutamatergic and GABAergic antagonists.... 63 5 Discussion 67 Chapter III Pressor effects on blood pressure induced by isovolumic bladder distension and electroacupuncture stimulation in anesthetized rats 73 1. Abstract 74 2. Introduction 75 3. Materials and methods 77 3-1 General operations 77 3-2 Electro-acupuncture stimulation 77 3-3 Cystrometry investigations 78 3-4 Statistical analysis 78 4 Results 79 4-1 Effects of electro-acupuncture at Hoku 79 4-2 Effects of Ea at Tsusani 79 4-3 Effect of bladder distension. 81 4-4 Combinations of the Eas and bladder distension. 81 5 Discussion 85 Remark 87 References 89 Ph.D. thesis related publication list 10

D-methionine alleviates cisplatin-induced mucositis by restoring the gut microbiota structure and improving intestinal inflammation

Background: There are close links between chemotherapy-induced intestinal mucositis and microbiota dysbiosis. Previous studies indicated that D-methionine was an excellent candidate for a chemopreventive agent. Here, we investigated the effects of D-methionine on cisplatin-induced mucositis. Materials and methods: Male Wistar rats (176–200 g, 6 weeks old) were given cisplatin (5 mg/kg) and treated with D-methionine (300 mg/kg). Histopathological, digestive enzymes activity, oxidative/antioxidant status, proinflammatory/anti-inflammatory cytokines in intestinal tissues were measured. Next-generation sequencing technologies were also performed to investigate the gut microbial ecology. Results: D-methionine administration increased villus length and crypt depth and improved digestive enzyme (leucine aminopeptidase, sucrose and alkaline phosphatase) activities in the brush-border membrane of cisplatin-treated rats ( p < 0.05). Furthermore, D-methionine significantly attenuated oxidative stress and inflammatory reaction and increased interleukin-10 levels in cisplatin-induced intestinal mucositis ( p < 0.05). Cisplatin administration resulted in high relative abundances of Deferribacteres and Proteobacteria and a low diversity of the microbiota when compared with control groups, D-methionine only and cisplatin plus D-methionine. Cisplatin markedly increased comparative abundances of Bacteroides caccae, Escherichia coli, Mucispirillum schaedleri, Bacteroides uniformis and Desulfovibrio C21-c20 , while Lactobacillus was almost completely depleted, compared with the control group. There were higher abundances of Lactobacillus , Lachnospiraceae, and Clostridium butyrium in cisplatin plus D-methionine rats than in cisplatin rats. D-methionine treatment alone significantly increased the number of Lactobacillus reuteri . Conclusion: D-methionine protects against cisplatin-induced intestinal damage through antioxidative and anti-inflammatory effects. By enhancing growth of beneficial bacteria (Lachnospiraceae and Lactobacillus ), D-methionine attenuates gut microbiome imbalance caused by cisplatin and maintains gut homeostasis