Continuous radio telemetry of hypothalamic temperatures from unrestrained animals

Abstract

A system of radio telemetry has been designed which continuously records body temperatures of unrestrained animals with a resolution of 0.05 C over transmission distances of 100ˑ1,000 ft, permitting observations on free-running animals for indefinite periods of time. Continuous 24-hr recordings were made of hypothalamic temperatures telemetered from cold-acclimatized and unacclimatized dogs living in cold, neutral, and hot environments. During night hours, dogs usually exhibited a decrease in hypothalamic temperature of 0.5ˑ.0 C below daylight levels. Superimposed on the day-night temperature cycle are marked fluctuations of 0.1ˑ0.5 C at a rate of 0.1 C/min. These variations are associated with the level of motor activity, arousal, and with periods of dozing. Shivering in the cold is exhibited even though hypothalamic temperature may be elevated above a level at which no shivering occurs in a neutral environment. spontaneous hypothalamic temperature variations; cold-acclimatized dogs; day-night temperature cycle Submitted on June 3, 1964