Abstract: AIM:To investigate the effects of psy- chological stress on ulcerative colitis rats and to explore the mechanisms of this ;meanwhile to investigate the ef- fects of anxiolytic drug on symptoms of ulcerative colitis rats under psychological stress and the mechanisms of it . METHODS:eighty male Wistar rats were randomly di- vided into four groups ( n =20) :UC control group ;UC stress group ;UC +clonazepam group ;UC stess +clonaz- epam group .After UC model was established with immu- nization, these rats were fightened by cat to set up psy- chological stress model .During establishing stress model, each groups were respectively received physiologic saline or clonazepam by intragastric administration .After 15d treatment, all rats were sacrified simultaneously .Colon mucosal inflammationand damage were assessed by mea- suring colon mass, morphologic damage score, colonic MPO and NO activity levels .Morphologic damage score was examined under microscope.Colonic MPO and NO was measured by spectrophotometric method .Serum hydrocortisone was determined by radioimmunoassay ( RIA) .RESULTS :Morphologic damage score, colonic MPO and NO, serum hydrocortisone of UC stress group were significantly increased compared with those of UC control group ;morphologic damage score, colonic MPO and NO, serum hydrocortisone of UC +clonazepam group were decreased markedly vs UC stress group ;Little differ- ence was observed between UC +clonazepam group and UC control group .CONCLUSION:Psychological stress can aggravate symptoms of UC.Although benzodiazepine have no anti-inflammatory action, it relieve effects on in- ternal organs of psychological stress and aggravation of symptoms of UC by to effect limbic system and formatio reticularis .

Key words: psychological stress ;ulcerative colitis , clonazepam ;rat