Objective      To determine the expression profiles of regulator of G protein signaling-4 (RGS4) and β-arrestin2 in the colon of rats with cathartic colon.       Methods      Twenty Wistar rats of either sex

weighing 200±20 g

were randomly divided into control group (

n

=8) and cathartic colon group (

n

=8)

. Control group were given soft chows

while the rats in cathartic group were given chows premixed with phenolphthalein powder to establish rat model with cathartic colon. RT-qPCR and Western blotting were adopted to detect the expression of RGS4 and β-arrestin2.       Results       Both RGS4 and β-arrestin2 expressed distinctly in the colon of cathartic group and control group. The results of RT-qPCR showed that both RGS4 and β-arrestin2 were expressed more intensively in cathartic colon group than in control group（3.418 3±0.247 4

vs

0.987 6±0.034 1

2.974 4±0.214 2

vs

0.921 1±0.040 1

P

<

0.01）. The results of Western blot assay showed that RGS4 and β-arrestin2 were expressed more intensively in cathartic colon group than in control group （0.403 4±0.049 9

vs

0.115 3±0.010  2，0.913 9±0.061 1

vs

0.467 6±0.043 7，

P

<

0.01）.       Conclusion        The up-regulated expression of RGS4 and β-arrestin2 in rats with cathartic colon indicate that the 2 proteins may play essential roles in the regulation of signal transduction of opioid receptor.