Abstract: AIM: To study the effects of ipratropium bromide (IB) with and without salbutamol (Sal) on the contraction of guinea pig tracheal strips induced by acetylcholine, histamine and potassium chloride in vitro.METHODS: The contraction of guinea pig tracheal strips induced by His, ACh and KCl before and after being incubated with ipratropium bromide;the contraction of guinea pig tracheal strips induced by His, and KCl before and after being incubated with salbutamol;the inhibitory effect of ipratropium bromide with salbutamol on the contraction of guinea pig tracheal strips induced by histamine and KCl.RESULTS: ACh (0.01^{- 1} mmol·L^-1) caused concentration-dependent contractions of tracheal strips and the resulting concentration-response curve was classical, the values of pD2 were 5.97 ±0.21, 6.48 ± 0.54, respectively.IB depressed the concentration-response curve with pD′2 values of 7.99 ±0.34 and 7.37±0.36, respectively.After adding Sal, the curve was further depressed.His (0.01 μmol·L^-1) caused the contraction of tracheal strips and its maximal response was obtained in 0.1 mmol·L^-1, the pD2 value was 6.60±0.70.After incubated with Sal, the concentration-response curve was depressed, and the pD′2 value was 6.06±0.27.Adding IB, the curve was further depressed. KCl (60 mmol·L^-1) induced contraction on tracheal strips, IB and Sal depressed the contraction with IC50 values of 4.78 ×10^-6 and 3.18 ×10^-6mol·L^-1, respectively.With combination of IB and Sal, the inhibitory effect was significantly enhanced (P<0.01).CONCLUSION: Either IB or Sal has a significant inhibitory effect on the contraction of tracheal strips induced by KCl, Ach and His.The effect is stronger in a combination with IB and Sal than that each alone.

Key words: ipratropium bromide, salbutamol, guinea pig, tracheal strip, acetylcholine