oa Southern African Journal of Anaesthesia and Analgesia - Local anaesthetic agent toxicity : regional anaesthesia
Local anaesthetic agents reversibly block the action potentials responsible for nerve conduction. This action is demonstrable in any part of the nervous system and on every type of nerve fibre.
The Na+ selective transmembrane pore of the channel is presumed to reside in the centre of a nearly symmetrical structure formed by the four homologous domains of a 300 kDa protein complex. A change in the transmembrane potential towards the threshold value induces conformational changes in the molecule, which cause the Na+ channel to open. This gives rise to a rapid influx of Na+ with further depolarisation of the cell membrane. After it opens, the Na+ channel inactivates within a few milliseconds due to closure of an inactivation gate.
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