A DISTURBED MACROCIRCULATORY SUPPLY AS A DETERMINANT FOR A REDUCED SCIATIC-NERVE BLOOD-FLOW IN DIABETIC RATS

The aim of this study was to evaluate macrocirculatory disturbances in relation to the reduced sciatic nerve blood flow seen in diabetic rat s. Therefore, both femoral blood flow, the macrocirculatory arterial b lood supply to the sciatic nerve, and the microcirculatory neuronal bl ood flow were measured. In order to differentiate between a direct vas cular or a neuronal defect as a cause for the disturbed macrocirculato ry blood flow the effects of the adrenocorticotropic hormone [ACTH]-(4 -9) analogue, Org 2766, a neurotrophic compound without cardiovascular effects, were investigated on the femoral flow under basal as well as adrenergic-stimulated conditions. Adrenergic responsiveness to tyrami ne and phenylephrine effect on femoral flow was determined. Basal scia tic nerve and femoral blood flow were reduced by 48% and 42%, respecti vely, after 12 weeks of diabetes, without effect on blood pressure. Tr eatment with Org 2766, beginning 6 weeks after the induction of diabet es, had no influence on these basal haemodynamic variables. Femoral fl ow in diabetic rats showed a smaller response to tyramine and phenylep hrine compared to the control. Org 2766 restored this disturbed flow r esponse to that of the control rats. In conclusion, the decrease in ba sal femoral flow might be responsible for the lowered sciatic nerve bl ood flow. Although neuronal disturbances due to diabetes had a very mi nor role in the reduction of basal femoral blood flow the adrenergic-s timulated flow responsiveness was seriously affected in diabetic rats.