title: Opioid receptors and associated regulator of G protein signaling are involved in the cathartic colon of rats.
abstract: A cathartic colon is characteristic of slow transit constipation (STC), which can result following the long-term use of irritant laxatives. In the present study, the involvement of three opioid receptor subtypes (μ, MOR; δ, DOR; and κ, KOR), regulator of G protein signaling 4 (RGS-4) and β-arrestin-2 were investigated in the cathartic colon of rats. A rat model of a cathartic colon was established by feeding the animals with phenolphthalein, while normal rats were used as a control. The mRNA and protein expression levels of the opioid receptors, RGS-4 and β-arrestin-2 were detected in the rat colon using semi-quantitative reverse transcription polymerase chain reaction and western blot analysis, respectively. The rat model of a cathartic colon was successfully established using the phenolphthalein stimulus, and was shown to result in shrunken myenteric neurons and loose muscle fibers in the intestinal wall. The mRNA and protein expression levels of the three opioid receptor subtypes, RGS-4 and β-arrestin-2 were significantly higher in the cathartic colon group when compared with the levels in the normal control group (all P<0.01). With regard to the protein expression levels, MOR protein increased 2.4 fold, DOR expression increased 1.5 fold, KOR levels increased 1.5 fold, RGS-4 protein increased 3.5 fold and β-arrestin-2 expression increased 2.0 fold. Therefore, the expression levels of opioid receptors were found to increase in the cathartic colons of the rats, indicating that opioid receptors and downstream RGS-4 and β-arrestin-2 signaling may play an important role in the pathogenesis of STC.
authors.affiliation: Department of General Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400042, P.R. China ; Second Department of General Surgery, Bethune International Peace Hospital of People's Liberty Army, Shijiazhuang, Hebei 050082, P.R. China.
authors.forename: Jinsong
authors.initials: J
authors.lastname: Wu
authors.affiliation: Department of General Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400042, P.R. China.
authors.forename: Baohua
authors.initials: B
authors.lastname: Liu
authors.affiliation: Department of General Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400042, P.R. China.
authors.forename: Weidong
authors.initials: W
authors.lastname: Tong
authors.affiliation: Department of General Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400042, P.R. China.
authors.forename: Anping
authors.initials: A
authors.lastname: Zhang
authors.affiliation: Department of General Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400042, P.R. China.
authors.forename: Fan
authors.initials: F
authors.lastname: Li
authors.affiliation: Department of Nephrology, Bethune International Peace Hospital of People's Liberty Army, Shijiazhuang, Hebei 050082, P.R. China.
authors.forename: Jing
authors.initials: J
authors.lastname: Lin
authors.affiliation: Department of General Surgery, Institute of Surgery Research, Daping Hospital, Third Military Medical University, Chongqing 400042, P.R. China.
authors.forename: L I
authors.initials: LI
authors.lastname: Wang
keywords: cathartic colon; constipation; opioid receptors; regulator of G protein signaling 4; β-arrestin-2