Increased Expression Of Mast Cell,SP And NK1 Receptor In The Rats Colon Of Chronic Visceral Hypersensitivity

Objective: To investigate the changes of expression of Mast cell (MCs), Substance P (SP) and NK1 receptor in the rats colon of chronic visceral hypersensitivity compared with control rats, discuss the possible mechanism of visceral hypersensitivity associated with irritable bowel syndrome (IBS).Methods: 40 SD rats were randomly divided into two groups: chronic irritation models and controls. The model was established by colorectal distention daily in the neonatal rats between postnatal 8 and 21 days. The threshold of abdominal withdrawal reflex (AWR) during rectal distension and the time of glass pellets output was evaluated at postnatal 8 and 12 weeks respectively, the expression of SP and NK1 receptor mRNA in the colon was studied by RT-PCR, the biopsies were stained specifically with histochemistry for the MCs and the distribution of NKl receptors were identified by Immunohistochemitry (IHC) in the colon wall of rats.Results: In contrast to the controls, chronic irritation models showed decrease in the threshold of AWR and time of glass pellets output; the levels of SP and NKl receptors mRNA was significantly increased; The number of the MCs was significantly elevated; The NK1-IR positive products were densely distributed in the smooth muscle layer and epithelium of colon wall of chronic irritation models.Conclusions: Increased expression of the MCs, SP and NKl receptor might plays a important role in the pathogenesis of visceral hypersensitivity associated with IBS in the chronic irritation models.