Duration-dependent variability in the responses of diabetic rat aorta to noradrenaline and 5-hydroxytryptamine.

1. The responsiveness of isolated aortic rings from 1, 4 and 12 week streptozotocin-induced diabetic rats to noradrenaline (NA) and 5-hydroxytryptamine (5-HT) were compared with those of non-diabetic controls under standard organ bath procedure. 2. There were significant increases in the maximum contractile responses to both agents after 1 and 4 weeks but not after 12 weeks of diabetes mellitus. 3. The variable responses show that duration-dependent functional changes occur in the course of streptozotocin diabetes in rats.