Inhibitory effect of tetrandrine on C fiber activation-induced contractions in trachea and bronchus of guinea pig.

AIM

To study the inhibitory effects of tetrandrine (Tet) on an activation of the sensory nervous C fibers in isolated trachea and bronchus of guinea pig.

METHOD

The electric field stimulation induced a phase II contraction of the preparations, which was due to an activation of the C fifers. The effects of Tet on phase II contraction were analyzed.

RESULTS

Tet 0.3-30 mumol.L(-1) inhibited phase II contractions in a concentration-dependent manner. That phase II contractions inhibited by Tet 1 mumol.L(-1) were 40 +/- 38% and 75 +/- 22% of control in tracheae and bronchi respectively. After pretreatment with chlorphenamine or atropine phase II contraction were still reduced by Tet 1 mumol.L(-1), inhibitory rates being 70 +/- 16% and 64 +/- 16% of control, respectively. The contractile responses of the preparations to exogenous substance P, however, were unaffected by treatment with Tet 1 mumol.L(-1).

CONCLUSION

Tet 1 mumol.L(-1) inhibits phase II contraction, related to the inhibition of local release of neuropeptides from C fibers of guinea pig airway.