Thermosensation

Abstract

Detection of temperature, both of the surroundings and of the body itself, is critical for maintaining normal physiological functioning. To date, a number of thermo‐sensitive ion channels have been reported to be involved in thermosensation, six of which belong to the transient receptor potential (TRP) superfamily of nonselective cation channels. Each of these operates over a distinct temperature range and many respond to natural compounds that elicit sensations of heat or cold. The best studied is TRP vanilloid 1 (TRPV1), which is both a receptor for capsaicin, the active principle of chilli peppers, and a painful heat receptor which responds to temperatures over 42°C. Our understanding of cold transduction has also rapidly increased in recent years with the intriguing discovery of the cold receptors TRP melastatin 8 (TRPM8) and TRP ankyrin 1 (TRPA1). Key concepts Our current understanding of thermosensation comes mainly from the identification of six temperature‐sensitive ion channels (thermo‐TRP channels) belonging to the transient receptor potential (TRP) superfamily of nonselective calcium channels. Each thermo‐TRP operates over a distinct temperature range. Four of them (TRPV1–4) are activated by heat, and two of them (TRPM8 and TRPA1) are activated by cold. Thermo‐TRPs also respond to natural compounds that elicit corresponding psychophysical sensations of heat or cold. The response of these channels is regulated after tissue damage and is subjected to modulation by inflammatory mediators released at the site of injury. The altered sensitivity of these channels accounts for the phenomenon of thermal hyperalgesia. Inflammatory mediators sensitize TRPV1 via the activation of protein kinases such as protein kinase C (PKC), protein kinase A (PKA) and Src. The modulation of TRPV1 by PKC and PKA depends on the correct positioning of the kinases by a scaffolding protein, AKAP79/150. There are other possible mechanisms involved in thermosensation, for example, modulation of potassium channels such as TREK‐2.

Effective gene expression in the rat dorsal root ganglia with a non-viral vector delivered via spinal nerve injection

“…The risk of variable expression levels of transduced genes in the DRG is another issue 13 16 , given that the DRG contains neurons of various sizes and phenotypes 20 21 22 , such as proprioceptors or thermal nociceptors 23 24 25 26 . Neurofilaments and peripherin are commonly used to assess large and small neurons, respectively 21 22 27 28 29 30 31 .…”