Effect of nitric oxide (NO) on dependence and tolerance of normorphine (NM) in the guinea-pig ileum in vitro / 中国药理学通报

ABSTRACT

AIM　To study the effect of NO on dependence and tolerance of NM in the guinea pig ileum in vitro. METHODS　The segment of the guinea pig ileum were suspended in organ chambers for measuring withdrawal responses are expressed as ratio of naloxone(100 nmol·L-1)and Ach (100 nmol*L-1) contraction respenses and measuring inhibitory effects of NM for contractions evoked by electric stimulation. RESULTS　After the segment of the ileum was incubated with NM (200 nmol*L-1), NM (200 nmol·L-1) plus L-Arg (0.1 mmol·L-1) ,at 4℃ for 24 h respectively, the ratio are 0.89±0.02, 0.90±0.02, (n=6) P>0.05. The ratio of NM (200 nmol·L-1) plus NOArg (0.1 mmol·L-1) is 0.47±0.05,compared with control (n=6,P<0.01). After the segment of the ileum was incubated with NM (500 nmol·L-1), NM (500 nmol·L-1) plus L-Arg (0.1 mmol·L-1) at 37℃ for 3 h respectively,the sensitivities of the preparations for NM were reduced significantly,their concentration-response curves were shift to right (P<0.01).In the segment of the ileum incubaled with NM (500 nmol·L-1) and NG-nitro-L-Arginime ( NOArg 0.1 mmol·L-1) at 37℃ for 3 h,the sensitivities of the preparations for NM was unchange (P>0.05).CONCLUSIONS　These results suggest that NO has important role on dependence and tolerance of NM in the guinea pig ileum.