title: Shugan-decoction relieves visceral hyperalgesia and reduces TRPV1 and SP colon expression.
abstract: OBJECTIVE
  To evaluate the therapeutic effect of Shugan-decoction (SGD) on visceral hyperalgesia and colon gene expressions using a rat model.
  
  
  METHODS
  Ninety-six adult male Wistar rats were randomized into six equal groups for assessment of SGD effects on psychological stress-induced changes using the classic water avoidance stress (WAS) test. Untreated model rats were exposed to chronic (1 h/d for 10 d consecutive) WAS conditions; experimental treatment model rats were administered with intragastric SGD at 1 h before WAS on consecutive days 4-10 (low-dose: 0.1 g/mL; mid-dose: 0.2 g/mL; high-dose: 0.4 g/mL); control treatment model rats were similarly administered with the irritable bowel syndrome drug, dicetel (0.0042 g/mL); untreated normal control rats received no drug and were not subjected to the WAS test. At the end of the 10-d WAS testing period, a semi-quantitative measurement of visceral sensitivity was made by assessing the abdominal withdrawal reflex (AWR) to colorectal balloon-induced distension (at 5 mmHg increments) to determine the pain pressure threshold (PPT, evidenced by pain behavior). Subsequently, the animals were sacrificed and colonic tissues collected for assessment of changes in expressions of proteins related to visceral hypersensitivity (transient receptor potential vanilloid 1, TRPV1) and sustained visceral hyperalgesia (substance P, SP) by immunohistochemistry and real-time polymerase chain reaction. Inter-group differences were assessed by paired t test or repeated measures analysis of variance.
  
  
  RESULTS
  The WAS test successfully induced visceral hypersensitivity, as evidenced by a significantly reduced AWR pressure in the untreated model group as compared to the untreated normal control group (190.4 ± 3.48 mmHg vs 224.0 ± 4.99 mmHg, P < 0.001). SGD treatments at mid-dose and high-dose and the dicetel treatment significantly increased the WAS-reduced PPT (212.5 ± 2.54, 216.5 ± 3.50 and 217.7 ± 2.83 mmHg respectively, all P < 0.001); however, the low-dose SGD treatment produced no significant effect on the WAS-reduced PPT (198.3 ± 1.78 mmHg, P > 0.05). These trends corresponded to the differential expressions observed for both TRPV1 protein (mid-dose: 1.64 ± 0.08 and high-dose: 1.69 ± 0.12 vs untreated model: 3.65 ± 0.32, P < 0.001) and mRNA (0.44 ± 0.16 and 0.15 ± 0.03 vs 1.39 ± 0.15, P < 0.001) and SP protein (0.99 ± 0.20 and 1.03 ± 0.23 vs 2.03 ± 0.12, P < 0.01) and mRNA (1.64 ± 0.19 and 1.32 ± 0.14 vs 2.60 ± 0.33, P < 0.05). These differential expressions of TRPV1 and SP related to mid- and high-dose SGD treatments were statistically similar to the changes induced by dicetel treatment. No signs of overt damage to the rat system were observed for any of the SGD dosages.
  
  
  CONCLUSIONS
  Shugan-decoction can reduce chronic stress-induced visceral hypersensitivity in rats, and the regulatory mechanism may involve mediating the expressions of TRPV1 and SP in colon tissues.
authors.affiliation: Jing-Juan Shang, Hui Xu, Rong-Zhu Tang, Yue-Bin Dong, Division of Gastroenterology, Shanghai Seventh People's Hospital, Shanghai 200137, China.
authors.forename: Jing-Juan
authors.initials: JJ
authors.lastname: Shang
authors.forename: Jian-Ye
authors.initials: JY
authors.lastname: Yuan
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
authors.forename: Rong-Zhu
authors.initials: RZ
authors.lastname: Tang
authors.forename: Yue-Bin
authors.initials: YB
authors.lastname: Dong
authors.forename: Jian-Qun
authors.initials: JQ
authors.lastname: Xie
mesh_terms: D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D003106:Colon / Q000187:drug effects / Q000294:innervation / Q000378:metabolism; D004195:Disease Models, Animal; D015536:Down-Regulation; D004365:Drugs, Chinese Herbal / Q000494:pharmacology*; D006930:Hyperalgesia / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D008297:Male; D017288:Pain Threshold / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012018:Reflex / Q000187:drug effects; D013315:Stress, Psychological / Q000150:complications; D013373:Substance P / Q000235:genetics / Q000378:metabolism*; D050916:TRPV Cation Channels / Q000235:genetics / Q000378:metabolism*; D017833:Visceral Afferents / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology
chemical_list: D000700:Analgesics; D004365:Drugs, Chinese Herbal; D012333:RNA, Messenger; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; D013373:Substance P
keywords: Shugan-decoction; Substance P; Sustained visceral hyperalgesia; Transient receptor potential vanilloid 1; Visceral hypersensitivity; Water avoidance stress