EFFECTS OF STREPTOZOTOCIN-DIABETES ON SYMPATHETIC-NERVE, ENDOTHELIAL AND SMOOTH-MUSCLE FUNCTION IN THE RAT MESENTERIC ARTERIAL BED

Mesenteric arterial function was assessed in constantly perfused prepa rations isolated from rats 12 weeks after treatment with streptozotoci n (65 mg kg(-1), i.p.) to induce diabetes. Frequency-dependent vasocon strictor responses to electrical field stimulation of sympathetic nerv es (4-32 Hz, 0.1 ms, 90V, 30 s) were severely attenuated in preparatio ns from streptozotocin-diabetic rats, although dose-dependent vasocons trictions to the sympathetic cotransmitters noradrenaline and ATP, as well as to potassium chloride, were not significantly changed. Dose-de pendent relaxations to the endothelium-dependent vasodilators acetylch oline and ATP were significantly impaired in preparations from strepto zotocin-diabetic rats, although endothelium-independent vasodilatation to sodium nitroprusside was unimpaired. These results suggest that 12 weeks after induction of streptozotocin-diabetes in rats there is pre -junctional impairment of sympathetic neurotransmission and impaired e ndothelial function of the mesenteric arteries. This is in contrast to our previous findings that at 8 weeks after induction of streptozotoc in-diabetes sympathetic nerve and endothelial function is normal, alth ough sensory-motor vasodilatation is severely attenuated. It is sugges ted that selective changes occur in mesenteric arterial function after streptozotocin treatment depending on the duration of diabetes; senso ry-motor nerves are affected first, followed by sympathetic nerves and the endothelium, while the smooth muscle is relatively resistant to c hange.