Objective      To explore a method of establishing interstitial cystitis (IC) in rats by intra-peritoneal injection of long-term low-dose cyclophosphamide (CYP)

and to determine the therapeutic effects of amitriptyline on IC.       Methods      A total of 42 Sprague Dawley rats were randomly divided into 7 groups

control

4-hour model group

48-hour model group

10-day model group

30-day model group

45-day model group and treatment group

with 6 rats in each group. The rats in IC model were treated with intraperitoneal injection of 40 mg/kg CYP once per 3 d. From the 31st day

the rats in treatment group wer

e given intragastrical injection of normal saline containing 10 mg·kg

-1

·d

-1

amitriptyline for 15 continuous days. After the rats were sacrificed at the corresponding time points

their bladder was taken for gross observation. The morphological changes of bladder tissue were observed by light microscopy and transmission electron microscopy. And the serum levels of IL-6

IL-10

and IL-17A were detected by enzyme linked immunosorbent assay (ELISA) in the control group

30-day model group

45-day model group and treatment group.       Results      The bladder of the model groups showed the morphological changes as the IC bladder. The levels of IL-6

IL-10

and IL-17A were significantly higher in the serum of 30-day and 45-day model groups than that of normal control (

P

0.05). But compared with 45-day model group

the levels in the treatment group were decreased (

P

0.05)

but still higher than those of the control group (

P

0.05).       Conclusion      Long-term low-dose CYP induces IC model in rats. Amitriptyline attenuates the bladder inflammatory responses in IC rats.