Thermographic imaging of mouse across circadian time reveals body surface temperature elevation associated with non-locomotor body movements.

Hiroyuki Shimatani,Yuichi Inoue,Masao Doi,Takahito Miyake,Yota Maekawa,Yoshiaki Yamaguchi,Nicolas Cermakian

doi:10.1371/journal.pone.0252447

Abstract

Circadian clocks orchestrate multiple different physiological rhythms in a well-synchronized manner. However, how these separate rhythms are interconnected is not exactly understood. Here, we developed a method that allows for the real-time simultaneous measurement of locomotor activity and body temperature of mice using infrared video camera imaging. As expected from the literature, temporal profiles of body temperature and locomotor activity were positively correlated with each other. Basically, body temperatures were high when animals were in locomotion. However, interestingly, increases in body temperature were not always associated with the appearance of locomotor activity. Video imaging revealed that mice exhibit non-locomotor activities such as grooming and postural adjustments, which alone induce considerable elevation of body temperature. Noticeably, non-locomotor movements always preceded the initiation of locomotor activity. Nevertheless, non-locomotor movements were not always accompanied by locomotor movements, suggesting that non-locomotor movements provide a mechanism of thermoregulation independent of locomotor activity. In addition, in the current study, we also report the development of a machine learning-based recording method for the detection of circadian feeding and drinking behaviors of mice. Our data illustrate the potential utility of thermal video imaging in the investigation of different physiological rhythms.

Highlights

Locomotor activity rhythm (LAR) and body temperature rhythm (BTR) have been used to detect circadian rhythms in living animals because they are both robust and easy to measure
By measuring body movement (BM) and body surface temperature (BST) with an infrared camera, we visualized previously unknown BST elevation in mice that occurred in close association with non-locomotor activity
Active locomotor movements were always preceded by non-locomotor activity-associated BST elevation, suggesting that non-locomotor activity and its associated body temperature elevation may be necessary for mice to initiate locomotor activity

Summary

Introduction

Locomotor activity rhythm (LAR) and body temperature rhythm (BTR) have been used to detect circadian rhythms in living animals because they are both robust and easy to measure. There are unfilled opportunities for the close analysis of LAR and BTR. LAR is usually detected by either an infrared sensor or a running wheel [1,2,3]. These methods cannot detect non-locomotor movements (i.e., activities that do not involve movement from place to place [4]), including feeding, drinking, grooming, and postural adjustments.

Methods

Results

Conclusion