Printed Poster | Session 2

045 – Circadian rhythm of somatosensation in inbred and outbred mice

Mitra Knezic (1) – Caitlin Lundell-Creagh (1) – Kaitlyn Tresidder (2) – Julia Segal (1) – Courtney Bannerman (1) – Ian Gilron (1, 2, 3) – Nader Ghasemlou (1, 2, 3)
Departments of Biomedical & Molecular Sciences and (1) – Departments of Anesthesiology & Perioperative Medicine (2) – Centre for Neuroscience Studies, Queen’s University, Kingston, Ontario, Canada (3)

Circadian (24-hour) rhythms affect many processes in the body including the sleep/wake cycle, hormone release, immune function, metabolic activity and core body temperature. Crosstalk between the nervous and immune systems underlie several functional and behavioural outcomes. Somatosensation – the transmission of sensory signals to the spinal cord and brain for processing – includes sensitivity to mechanical, thermal and nociceptive stimuli, propagated by distinct populations of sensory neurons. These sensory neuron subsets can be identified by their expression of specific ion channels and receptors including receptor tyrosine kinases, G-protein coupled receptors, and ion channels. Non-specific cation channels of the transient receptor potential (TRP) family confer specific modalities to sensory neurons. TRPV1, for instance, is activated by heat and capsaicin, the active ingredient in chili peppers. We sought to characterize the circadian rhythm of somatosensation in naïve mice. Our work shows that thermal somatosensation exhibits a circadian rhythm and that heat sensitivity is significantly reduced in male C57BL/6J mice during the dark phase relative to the light phase, whereas female mice do not show this effect. Due to the limited phenotypic variability associated with inbred strains, we also sought to determine if this effect is reproducible in an outbred stain, using CD1 mice, where individual mice show greater genetic and phenotypic diversity. A similar circadian variation in thermal sensitivity was also maintained in these mice, with a more prominent effect in males than females. Quantitative PCR of TRP channels in the spinal cord and dorsal root ganglia reveal few circadian changes in expression in C57BL/6J mice, suggesting that other mediators/channels may play a role in this response. Our results show a modality-specific circadian rhythm of somatosensation in inbred and outbred mouse strains, without an altered TRP channel response. Identifying potential mediators of this response may help our understanding of somatosensory function.