Expression of TRPV1 and Electrophysiological Characteristics of Colon-specific Dorsal Root Ganglion Neurons in Rat Model of Visceral Hypersensitivity / 胃肠病学

ABSTRACT

Background:Visceral hypersensitivity is considered to be one of the major pathophysiological mechanisms of irritable bowel syndrome. Aims:To investigate the expression of TRPV1 and electrophysiological characteristics of colon-specific dorsal root ganglion( DRG)neurons in rat model of visceral hypersensitivity. Methods:Twenty 10-day-old rats were randomly divided into two groups. In model group,visceral hypersensitivity was induced by colorectal administration of acetic acid;while in control group the same amount of saline was administered. Colon-specific DRG neurons were labeled retrogradely by injection of DiI,a fluorochrome,into the colon wall. Expression of TRPV1 in DRG neurons was detected by immunofluorescence and the electrophysiological characteristics of DRG neurons was detected by using patch-clamp technique. Results:In model group,the expression rate of TRPV1 in colon-specific DRG neurons was significantly higher than that in controls(46. 1% vs. 36. 6% ,P <0. 01),the average rheobase was significantly decreased[(57. 80 ±1. 32)pA vs.(73. 45 ± 4. 51)pA,P < 0. 05],while the frequency of action potentials(APs)in response to doubling rheobase stimulation was significantly increased[(8. 20 ± 1. 10)Hz vs. (4. 54 ± 0. 66)Hz,P < 0. 05]. Score of abdominal withdrawal reflex(AWR)under a 60 mm Hg colorectal distention was positively correlated with the expression rate of TRPV1 and the frequency of APs in response to doubling rheobase stimulation(r = 0. 87 and r = 0. 73,P < 0. 01),but was negatively correlated with the rheobase(r = - 0. 81,P < 0. 01)in model group. Conclusions:Increased expression of TRPV1 and excitability in colon-specific DRG neurons might be a crucial step in formation of visceral hypersensitivity.