Rat tail skin temperature monitored noninvasively by radiotelemetry: characterization by examination of vasomotor responses to thermomodulatory agents.

INTRODUCTION: Measurement of tail skin temperature (T(sk)) of the rat can provide important information on mechanisms pertaining to physiology, pharmacology, and toxicology. T(sk) is largely under control of peripheral vascular tone, which is also sensitive to most experimental manipulations such as handling and restraint. Hence, it is extremely difficult to acquire long-term measurements of T(sk) that are free of artifacts from experimental manipulation. The purpose of this study is to demonstrate the utility of a radiotelemetric probe to provide continuous, long-term measurements of T(sk) in undisturbed rats.
METHODS: A telemetry probe is placed on the base of the tail and secured with a protective guard to prevent the rat from chewing on the probe. T(sk) is continuously monitored with standard radiotelemetric software and computer technology. Core temperature (T(c)) is monitored in duplicate sets of rats at the same time but the current system does not allow for simultaneous measurement of T(sk) and T(c) from the same animal. Rats were subjected to a variety of experimental manipulations to demonstrate the utility of the probe. RESULTS/DISCUSSION: A marked increase in T(sk) was seen during the transition from light to dark phase, reflecting an increase in heat loss to lower T(c); a decrease in T(sk) during the development of endotoxin-induced fever, reflecting a reduction in heat loss to facilitate an elevation in T(c); an increase in T(sk) following exposure to the organophosphate insecticide chlorpyrifos, reflecting an increase in heat loss to facilitate a hypothermia response; and a direct effect of increasing ambient temperature on T(sk). The probe is relatively inexpensive and is used with no surgery and provides long-term measurement (e.g., >24 h) of T(sk) in unrestrained rats.