In the present study, the contractile effects of acetylcholine (Ach) were investigated in isolated tracheal strips obtained from insulin-dependent (ID) and non-insulin-dependent (NID) diabetic rats. 2. The maximum responses to Ach were significantly decreased in 5-6 week ID diabetic rat tracheal segments compared with those from controls but, the sensitivity (pD2 values) of ID diabetic tracheas to Ach were not significantly altered relative to corresponding controls. 3. Tracheas isolated from 11-12 week NID diabetic rats exhibited reduced maximal contractile effect of Ach and also sensitivity (pD2 values) of NID diabetic tracheas to Ach were significantly decreased when compared to control rat tracheas. 4. Insulin treatment of both group of diabetic rats for 10 days corrected the changes observed in diabetic tracheas.
