Cardiac and thermoregulatory responses to inhaled pollutants in healthy and compromised rodents: modulation via interaction with environmental factors.

Rodents often demonstrate a profound depression in physiological function following acute exposure to toxic xenobiotic agents. This effect, termed the hypothermic response, is primarily characterized by significant decreases in core temperature and heart rate and is generally accompanied by similar deficits in other important functional parameters. This response appears to be remarkably consistent across a wide variety of toxic agents and exposure regimens; however, the magnitude and duration of the induced effects may be modulated by changes in dose, animal mass, and environmental conditions. While the initiating stimulus and underlying mechanism(s) remains elusive, this response may represent an inherent reflexive pattern that is unique to the rodent and serves to attenuate the induced toxicity. Given that rodents are the primary animal species used in toxicological studies, it is important to consider this hypothermic response and its modulatory factors when interpreting the results of such studies and extrapolating those results to man.