Circadian Rhythm of Somatosensation

Abstract

Circadian rhythm is now well established for a broad range of behavioural, psychological, and physiological variables. This is known to be regulated by master pacemaker in the brain. In recent years, the diurnal variations in a variety of syndromes associated with painful disease have received much scrutiny. The objective of the present study is to address the controversial issue over the existence of diurnal variations in pain perception. Behavioural analysis showed the diurnal variation of pain and mechanosensation in normal wild-type mice. Cultured dorsal root ganglia (DRG) neurons exhibited a temporal change of neuronal excitability with a dramatic increase of firing frequency in the afternoon, suggesting endogenous temporal control of somatosensory transduction. Analysis of DRG-specific ion channel identified temporal variations in expression of TRPV1 and Nav1.6 that may contribute to changes of firing frequencies of sensory DRG neurons. These findings suggest essential roles of peripheral sensory neurons in circadian variation of pain perception that is regulated by endogenous clock-controlled pathways. It raises a potential chronotherapeutic approaches to the treatment of pain.