Tetrodotoxin‐resistant impulses in single nociceptor nerve terminals in guinea‐pig cornea

Open Access
Publisher Website
Google Scholar
Abstract
1 Extracellular recording techniques have been used to study nerve impulses in single sensory nerve terminals in guinea-pig cornea isolated in vitro. 2 Nerve impulses occurred spontaneously and were evoked by electrical stimulation of the ciliary nerves. 3 The nerve impulses were identified as originating in polymodal receptors, mechano-receptors or ‘cold’ receptors. All three types are believed to be nociceptors. 4 Tetrodotoxin (TTX, 1 μm) blocked nerve impulses evoked by electrical stimulation of the ciliary nerves. However, ongoing and/or naturally evoked nerve impulses persisted in the presence of TTX in all three types of receptors. Lignocaine (lidocaine; 1 mm) blocked all electrical activity. 5 TTX-resistant sodium channels therefore play a major role in generating the action potentials that signal pain to the brain.