Fast calcium and voltage–sensitive dye imaging in enteric neurones reveal calcium peaks associated with single action potential discharge

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Abstract

Non–technical summary

Imaging of slow, long–lasting changes in intracellular Ca2+ levels ([Ca2+]i) is a common method to assess neuronal activity. We found that fast [Ca2+]i imaging (≥200 Hz sampling rate) may be a new option to record fast neuronal events including spike discharge and fast synaptic transmission in enteric neurones. These [Ca2+]i peaks required opening of voltage–gated sodium and calcium channels as well as Ca2+ release from intracellular stores.

Slow changes in [Ca2+]i reflect increased neuronal activity. Our study demonstrates that single–trial fast [Ca2+]i imaging (≥200 Hz sampling rate) revealed peaks each of which are associated with single spike discharge recorded by consecutive voltage–sensitive dye (VSD) imaging in enteric neurones and nerve fibres. Fast [Ca2+]i imaging also revealed subthreshold fast excitatory postsynaptic potentials. Nicotine–evoked [Ca2+]i peaks were reduced by ω–conotoxin and blocked by ruthenium red or tetrodotoxin. Fast [Ca2+]i imaging can be used to directly record single action potentials in enteric neurones. [Ca2+]i peaks required opening of voltage–gated sodium and calcium channels as well as Ca2+ release from intracellular stores.

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