Possible therapeutic effects of essential oils on voltage dependent Na⁺ channels in experimental diabetic neuropathy

Diabetic neuropathy (DN) is the most frequent complication of diabetes mellitus (DM), characterized by derangements of somatic and autonomic nerves, predominantly the longest nerves. DN is clinically relevant because it may seriously damage the quality of life of the patient, may be life-threatening, and is of great epidemiological incidence. It causes severe pain, dysesthesia, and allodynia initially; with disease progression, it kills the nerve, leading to full anaesthesia, accidental feet, leg ulceration, diabetic foot, and amputation. Underlying these dysfunctional alterations, there are nerves and neurosomes electrophysiological alterations, which mechanism knowledge will likely disclose therapeutic targets offering opportunities for the development of new medicines. The electrophysiological derangements include alteration of excitability, of velocity of conduction, and of the inward Na⁺ current that causes the neuronal action potential. There is no specific treatment for DN. Investigation of the Laboratory of Electrophysiology (LEF) of Ceará State University, Ceará, Brazil, has discovered several DM-induced neural alterations. It has also discovered that the essential oil of the Croton zehntneri (a plant of the biome caatinga of Northeast of Brazil), and its major chemical constituent, anethole, is able to fully prevent some important electrophysiological neural alterations of experimental DN without hyperglycaemia correction. This prevention without restoration to euglycaemia suggests the usefulness of this essential oil and anethole as a medicine complementary to hypoglycaemic agents for the treatment of DN. These results, together with discoveries from other laboratories that are specifically related to the results of LEF investigation will be presented in this chapter.