Water deprivation reveals early neuromyopathy in diabetic mice

The effects of water deprivation on peripheral nerve and muscle function we re investigated in flexor digitorum superficialis muscle of control and dia betic mice. Twenty mice (30 g average body weight) were injected once with streptozotocin solution (200 mg/kg) to induce experimental diabetes and ano ther 20 mice of similar body weight served as controls. Two weeks later, co mparative analyses of in situ muscle isometric contractile characteristics were performed by direct muscle stimulation and indirect nerve stimulation (at 1, 5 and 30 Hz) in urethane-anesthetized (2 mg/g, i.p.) control and dia betic mice. One day prior to the experiments, 10 control and 10 diabetic mi ce were deprived of water. The study contained four groups: hydrated (H) co ntrol, dehydrated (DH) control, H diabetic and DH diabetic. There were no s ignificant differences in synaptic delay or twitch tension between Fl contr ol and DH control. Comparing H control and H diabetic groups, no difference s were noticed in synaptic delay or twitch tension; except at 30 Hz where t witch tension was reduced in H diabetic mice. Significant differences were observed when comparing DH control and DH diabetic mice. DH diabetic showed a significant increase in synaptic delay (from 7.4 to 9.3 ms) and a signif icant decrease in twitch tension evoked either by indirect nerve or by dire ct muscle stimulation (from 4.4 g to 1.9 g and from 4.4 g to 2.3 g, respect ively). These results revealed that water deprivation enhances diabetes eff ects at the neuromuscular junction and at the muscle leading to further com plication of neuromyopathy.