Abstract

Free nerve endings are key structures in sensory transduction of noxious stimuli. In spite of this, little is known about their functional organization. Transient receptor potential (TRP) channels have emerged as key molecular identities in the sensory transduction of pain-producing stimuli, yet the vast majority of our knowledge about sensory TRP channel function is limited to data obtained from in vitro models which do not necessarily reflect physiological conditions. In recent years, the development of novel optical methods such as genetically encoded calcium indicators and photo-modulation of ion channel activity by pharmacological tools has provided an invaluable opportunity to directly assess nociceptive TRP channel function at the nerve terminal.

Highlights

  • In mammals, environmental information is predominantly relayed by peripheral neurons of the somatosensory system

  • This article provides an overview of the latest optical tools applied in optical control and optical recording of nociceptive transient receptor potential (TRP) channel activity at the nerve terminal

  • In addition to transducer channels that underlie the receptor potential generation, sensory nerve fibers express a large variety of voltage- and ligand-gated ion channels, primarily voltage-gated sodium channels (Navs), voltage-gated potassium channels (Kvs), voltagegated calcium channels (VGCCs), and hyperpolarization-activated cyclic nucleotide–gated (HCN) channels

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Summary

Introduction

Environmental information is predominantly relayed by peripheral neurons of the somatosensory system. The main component of our knowledge on transducer TRP channel function at the nerve terminal has been inferred from experimental data obtained from in vitro transduction models lacking physiological conditions such as cell lines heterologously expressing TRP channels or cultured primary sensory neurons [16] This provided invaluable information on the roles TRP channels play in nociception, the possible alteration of expression, distribution, and modulation by endogenous factors of TRP channels under non-physiological conditions [17,18], and other factors such as distinct morphology between the nerve terminal and soma, might account for different coding of noxious stimuli by TRP channels in their physiological environment. This article provides an overview of the latest optical tools applied in optical control and optical recording of nociceptive TRP channel activity at the nerve terminal

Nociceptive TRP Channels at Sensory Nerve Fibers
TRP Channels at Skin Nerve Endings
TRP Channels at Corneal Nerve Terminals
Opto-Pharmacological Control of Nociceptive TRP Channel Activity at the
Testing Method
Optical Recording of Nociceptive TRP Channel Activity at the Nerve Terminal
Findings
Concluding Remarks
Full Text
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