Effect Of TRPA1on Visceral Hypersensitivity In Maternal Separation Rats

Objectives：To explore the effect of TRPA1on visceral hypersensitivity in maternalseparation (MS) rats by observing the TRPA1expression in DRG, and to explore therelationship with the visceral hypersensitivity, and the expression of CGRP,SP inspinal dorsal horn.Methods：According to the factorial design,32neonatal male SD rats were randomlydivided into four groups:(1)Group A1B1, bred normally and had intraperitonealinjection of normal saline(NS) before CRD;(2)Group A1B2, bred normally and hadintraperitoneal injection of ruthenium red(iRR) before CRD;(3)Group A2B1, MS andintraperitoneal injection of NS;(4)Group A2B2,MS and iRR.Eight weeks after MS,visceral hypersensitivity was elavuated by AWR andelectromyography of external oblique of abdomen（EEOA） with CRD. The distalcolon tissues were collected for histopathologic examinations. The expression ofTRPA1in DRG, and the expression of CGRP,SP in the spinal dorsal horn weredetected by the immunohistochemical staining.Results:(1)When the CRD pressure was40mmHg,60mmHg and80mmHg respectively,the main effect of MS on the AWR was0.22,0.57and0.35, among which thedifference had statistic significance (p=0.036,0.009and0.027, respectively). Whenthe CRD pressure was40mmHg,60mmHg respectively,the main effect of iRR on theAWR was-0.22and-0.44. Similarly, the difference had statistic significance(p=0.036and0.039respectively). On the20mmHg，40mmHg,60mmHg，80mmHg of CRDpressure respectively, there was no significant interactive effect of MS and iRR on theAWR score(p=0.361,0.128,0.352and0.130, respectively)；(2)On40mmHg,60mmHg and80mmHg of CRD pressure, the main effect of MSon the EEOA was5.56,7.88and12.55, respectively. The difference had statistic significance(p=0.000,0.000and0.000，respectively).On60mmHg,80mmHg of CRDpressure, the main effect of iRR on the EEOA was-4.35and-4.74,respectively. Thedifference had statistic significance(p=0.003and0.039, respectively).On20mmHg,40mmHg,60mmHg,80mmHg of CRD pressure, there was no significant interactiveeffect of MS and iRR on the EEOA (p=0.744、0.931、0.062and0.572，respectively)；(3)The main effect of MS on the mean optical density of TRPA1in DRG andCGRP,SP in the spinal dorsal horn were0.0577,0.1484and0.1726,respectively,thedifference had statistic significance(p=0.001,0.000and0.000,respectively).The maineffect of iRR on the mean optical density of TRPA1in DRG and CGRP,SP in thespinal dorsal horn were-0.0210,-0.01113and-0.0121,respectively,the difference hadstatistic significance(P=0.186,0.509and0.579,respectively). There was no significantinteractive effect of MS and iRR on the mean optical density of TRPA1in DRG, or onthe expression of CGRP, SP in the spinal dorsal horn (p=0.321,0.936and0.777,respectively)；(4)There was a positive relationship between the mean optical density of TRPA1and SP, or and CGRP, or AWR scores, or the EEOA (p<0.05, respectively). Likewise,The mean optical density of SP, or CGRP showed a positive relationship with theAWR scores, or the EEOA (p<0.05,respectively).Conclusions：These results indicated that maternal separation may induce visceralhypersensitivity in rats. The overexpression of TRPA1may involve in thepathogenesis of visceral hypersensitivity in these rats.