Objective    To study the expression of β-adrenoceptor in interstitial cells of Cajal (ICC) of guinea-pig ureters and its function.   Methods   Guinea pigs were divided into control group and experimental group. Changes in ureteral muscle contraction amplitude and frequency of ureteral muscle contraction after treatment with  β-adrenergic agonist

were observed. Expression of β-adrenergic receptor subtypes (β1

β2 and β3) in ICC of guinea-pig ureters was detected using immunofluorescence double labeling technique.  Results   After treatment with isoprenaline

the ureteral muscle contraction amplitude and the frequency of ureteral muscle contraction were significantly lower in control than in experimental group（0.070±0.035 vs 0.100±0.028

7.200±3.580 vs 2.480±1.21

P0.05）

indicating that the relaxing action of isoprenaline on ureteral muscle was greater in control group than in experimental group. Immunofluorescence double labeling showed that β3 receptor subtypes were expressed only in ureteral ICC. After treatment with selective β3-adrenergic agonist （CGP12177）

the ureteral muscle contraction amplitude and the frequency of ureteral muscle contraction were significantly lower in control group than in experimental group （0.068±0.023 vs 0.115±0.031

3.870±0.474 vs 6.410±1.895

P0.05）

showing that the relaxing action of CGP12177 on ureteral muscle was weaker in experimental group than in control.   Conclusion Noradrenergic nerves can regulate the ureter contraction and relaxation by activating the β3 adrenergic receptor subtypes of ICC.