Pathophysiology of the neuromuscular junction in diabetic rats

Using electrophysiological methods, we examined transport and transmission properties of the neuromuscular synapse in normal and diabetic rats. The stereospecific glucose transport system in the presynaptic nerve terminal was examined in two diabetic models and compared to the control. In both the streptozotocin (STZ) model and the Cohen model, a significant reduction was observed in the rates of glucose transport. A semiquantitative index for glucose transport, the glucose uptake factor, was 61 +/- 18% (SD) in the control group, 17 +/- 9% in the STZ group, and 15 +/- 10% in the Cohen group. Diabetes also affects the liberation of acetylcholine from the presynaptic motor nerve endings. The mean number of acetylcholine quanta liberated by the nerve impulse [quantal content (QC)] was reduced by 43% after 3.5 months of STZ diabetes. Thus, both the metabolic and the transmission functions of the neuromuscular junction are affected by the diabetic state.