A refined method to monitor arousal from hibernation in the European hamster

Fredrik A F Markussen,Shona H Wood,Vebjørn J Melum,Valérie Simonneaux,David G Hazlerigg,Béatrice Bothorel

doi:10.1186/s12917-020-02723-7

Abstract

BackgroundHibernation is a physiological and behavioural adaptation that permits survival during periods of reduced food availability and extreme environmental temperatures. This is achieved through cycles of metabolic depression and reduced body temperature (torpor) and rewarming (arousal). Rewarming from torpor is achieved through the activation of brown adipose tissue (BAT) associated with a rapid increase in ventilation frequency. Here, we studied the rate of rewarming in the European hamster (Cricetus cricetus) by measuring both BAT temperature, core body temperature and ventilation frequency.ResultsTemperature was monitored in parallel in the BAT (IPTT tags) and peritoneal cavity (iButtons) during hibernation torpor-arousal cycling. We found that increases in brown fat temperature preceded core body temperature rises by approximately 48 min, with a maximum re-warming rate of 20.9℃*h-1. Re-warming was accompanied by a significant increase in ventilation frequency. The rate of rewarming was slowed by the presence of a spontaneous thoracic mass in one of our animals. Core body temperature re-warming was reduced by 6.2℃*h-1 and BAT rewarming by 12℃*h-1. Ventilation frequency was increased by 77% during re-warming in the affected animal compared to a healthy animal. Inspection of the position and size of the mass indicated it was obstructing the lungs and heart.ConclusionsWe have used a minimally invasive method to monitor BAT temperature during arousal from hibernation illustrating BAT re-warming significantly precedes core body temperature re-warming, informing future study design on arousal from hibernation. We also showed compromised re-warming from hibernation in an animal with a mass obstructing the lungs and heart, likely leading to inefficient ventilation and circulation.

Highlights

Hibernation is a physiological and behavioural adaptation that permits survival during periods of reduced food availability and extreme environmental temperatures
We demonstrate that increases in to monitor both BAT temperature (TBAT) precede increases in Core body temperature (Tb) and that the ventilation frequency correlates with the rate of TBAT rewarming
Re-warming in brown fat compared to the core body We placed Implantable Programmable Temperature Transponder (IPTT) tags subcutaneously to measure the TBAT

Summary

Introduction

Hibernation is a physiological and behavioural adaptation that permits survival during periods of reduced food availability and extreme environmental temperatures This is achieved through cycles of metabolic depression and reduced body temperature (torpor) and rewarming (arousal). This is achieved through cycles of metabolic depression characterised by reduced body temperature (torpor) and Markussen et al BMC Veterinary Research (2021) 17:14 temperature increases in brown fat correlate with increased oxygen consumption (respiration rate) in the brown bat (Eptesicus fuscus) and the golden-mantled ground squirrel (Callospermophilus lateralis), and precede rectal or muscle temperature increases [7,8,9,10]. These data highlight the importance of non-shivering thermogenesis by BAT in the initial stages of the re-warming process

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