Objective       To determine the expression of 3 subtypes of opioid receptors

μ (mu-opioid receptor

MOR)

δ (delta-opioid receptor

DOR)

and κ (kappa-opioid receptor

KOR)

in the colon of rats with cathartic colon.       Methods      Twenty Wistar rats of either sex at an age of 7 to 6 weeks

weighing 200±20 g were randomly divided into control group (

n

=10

fed with normal chow) and cathartic colon group [

n

=10

fed with 3 cycles of 200 mg/(kg·d) phenolphthalein first and then increased by this dose till 80% of rats having loose stool disappeared

]

. RT-qPCR and Western blotting were adopted to detect the expression of the 3 subtypes of opioid receptors.       Results      All 3 subtypes of opioid receptor were expressed distinctly in the colon between cathartic group and control group. RT-qPCR indicated that the expression of MOR

DOR and KOR at mRNA levels were significantly higher in cathartic colon group than in control group (5.093±1.410

vs

1.092±0.222

2.612±0.612

vs

1.032±0.082

2.607±0.327

vs

0.995±0.109

P

<

0.01). While Western blot analysis showed their protein levels were in consistence with their mRNA levels between the 2 groups (0.361±0.023

v

s 0.152±0.021

0.246±0.059

vs

0.159±0.005

0.309±0.018 vs 0.201±0.015

P

<

0.01)

showing that all 3 subtypes of opioid receptor expressed more intensively（

P

<

0.001）.       Conclusion      Three subtypes of opioid receptors are enhanced in the cathartic colon

suggesting that colonic motility and secretion are significantly suppressed in slow transit constipation.