title: TRPA1 in the spinal dorsal horn is involved in post-inflammatory visceral hypersensitivity: in vivo study using TNBS-treated rat model.
abstract: BACKGROUND
  The transient receptor potential ankyrin-1 (TRPA1) channel, a pain transducer and amplifier, is drawing increasing attention in the field of visceral hypersensitivity, commonly seen in irritable bowel syndrome and inflammatory bowel disease. However, the role of TRPA1 in visceral nociception during post-inflammatory states is not well defined. Here, we explore the correlation between TRPA1 expression in the spinal dorsal horn (SDH) and persistent post-inflammatory visceral hypersensitivity.
  
  
  METHODS
  We injected rats intracolonically with 2,4,6-trinitrobenzene sulfonic acid (TNBS) or vehicle (n=12 per group). Post-inflammatory visceral hypersensitivity was assessed by recording the electromyographic activity of the external oblique muscle in response to colorectal distension. TRPA1 expression and distribution in the spinal cord and colon were examined by Western blotting and immunohistochemistry.
  
  
  RESULTS
  Animals exposed to TNBS had more abdominal contractions than vehicle-injected controls (P<0.05), which corresponded to a lower nociceptive threshold. Expression of TRPA1 in the SDH (especially in the substantia gelatinosa) and the colon was significantly greater in the TNBS-treated group than in controls (P<0.05). In the SDH, the number of TRPA1-immunopositive neurons was 25.75±5.12 in the control group and 34.25±7.89 in the TNBS-treated group (P=0.023), and integrated optical density values of TRPA1 in the control and TNBS-treated groups were 14,544.63±6,525.54 and 22,532.75±7,608.11, respectively (P=0.041).
  
  
  CONCLUSIONS
  Our results indicate that upregulation of TRPA1 expression in the SDH is associated with persistent post-inflammatory visceral hypersensitivity in the rat and provides insight into potential therapeutic targets for the control of persistent visceral hypersensitivity.
authors.affiliation: Department of Gastroenterology, Qilu Hospital of Shandong University.
authors.forename: Qian
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Pathology, Medical School of Shandong University.
authors.forename: Cheng-Hao
authors.initials: CH
authors.lastname: Guo
authors.affiliation: Department of Gastroenterology, Qilu Hospital of Shandong University.
authors.forename: Mohammed Ali
authors.initials: MA
authors.lastname: Chowdhury
authors.affiliation: Department of Gastroenterology, Qilu Hospital of Shandong University.
authors.forename: Tao-Li
authors.initials: TL
authors.lastname: Dai
authors.affiliation: Department of Gastroenterology, Qilu Hospital of Shandong University; Laboratory of Translational Gastroenterology, Shandong University, Qilu Hospital, Jinan, Shandong Province, People's Republic of China.
authors.forename: Wei
authors.initials: W
authors.lastname: Han
keywords: TRPA1; post-inflammatory visceral hypersensitivity; spinal dorsal horn; substantia gelatinosa