Defective activity of Na+,K(+)-ATPase in peripheral nerve of diabetic rats is independent of the axonal transport of the enzyme

Moderate hypoglycemia aggravates effects of hypoxia in hippocampal slices from diabetic rats

We recorded the effects of hypoxia combined with relative hypoglycemia on pre- and post-synaptic potentials in the CA1 area of slices from 4-month-old control and diabetic (streptozotocin-treated) Wistar rats. In experiments on slices kept in 10 or 4 mM glucose (at 33 degrees C), hypoxia was applied until the pre-synaptic afferent volley disappeared--after 12-13 min in most slices, but much earlier (5+/-0.8 min) in diabetic slices kept in 4 mM glucose. When oxygenation was resumed, the afferent volley returned in all slices, for an overall mean recovery of 86.5% (+/-8.8%). Field post-synaptic potentials were fully blocked within 2-3 min of the onset of hypoxia. After the end of hypoxia, they failed to reappear in some slices: overall, their recovery varied between 62 and 68% in control slices, as well as in diabetic slices kept in 10 mM glucose; but recovery was very poor in diabetic slices kept in 4 mM glucose (only 15+/-0.94%). In the latter, hypoxic injury discharges occurred earlier (4.2+/-0.68 min vs. 6.5-8 min for other groups). We conclude that diabetes appears to make hippocampal slices more prone to irreversible loss of synaptic function and early block of axonal conduction when temporary hypoxia is combined with moderate hypoglycemia.

The role of axonal ion conductances in diabetic neuropathy: a review

Diabetic neuropathy is a common complication in diabetes mellitus. Diabetic neuropathy is accompanied by alterations in axonal excitability, which can lead to either "positive" (paresthesia, dysesthesia, pain) and/or "negative" (hypesthesia, anesthesia) symptoms. The mechanisms underlying these alterations in axonal excitability are not well understood. Clinical tests reveal reduced nerve conduction velocity and axonal loss, but fail to explain nerve excitability. Many different factors have been suggested in relation to the pathophysiology of diabetic neuropathy. There are probably as many factors as there are different clinical pictures in diabetic neuropathy. Nevertheless, it seems that hyperglycemic hypoxia is mainly responsible for the electrophysiological changes seen in damaged diabetic nerves. This article summarizes experimental data indicating that a dysfunction of ion conductances, especially voltage-gated ion channels, could contribute to abnormalities in the generation and/or conduction of action potentials in diabetic neuropathy.