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EFFECT OF MARINE TOXINS ON THERMOREGULATION IN MICE.
Citation:
Gordon, C J. EFFECT OF MARINE TOXINS ON THERMOREGULATION IN MICE. Presented at Behavioral Toxicology Society, Philadelphia, PA, 6/21-26/03.
Description:
Marine algal toxins are extremely toxic and can represent a major health problem to humans and animals. Temperature regulation is one of many processes to be affected by exposure to these toxins. Mice and rats become markedly hypothermic when subjected to acute exposure to the marine toxins maitotoxin (MTX) and brevetoxin (BTX). When given the option to behaviorally thermoregulate by housing mice in a temperature gradient, mice dosed with MTX and BTX prefer cooler temperatures concomitant with hypothermia. This suggests that the hypothermic response is regulated by CNS thermoregulatory centers. Thermal dysthesia, characterized by a painful sensation of cool surfaces, is a common ailment in humans exposed to BTX and ciquatoxin. There is no animal model to study thermal dysthesia and little is known on the mechanism of action. This laboratory developed a behavioral system to assess the possible development of thermal dysthesia in mice exposed to BTX. Female mice were implanted with radio transmitters to monitor core temperature (Tc) and motor activity (MA). In one experiment, mice were dosed with the control vehicle or 180 g/kg BTX (IP) and placed in a temperature gradient to measure the selected foot temperature (SFT) while air temperature was kept constant. BTX-treated mice underwent a 10 C reduction in SFT concomitant with a 3 C reduction in Tc. In a second study, Tc and MA were monitored in mice maintained in their home cages after dosing with 180 g/kg BTX. Tc but not MA increased for 2 to 5 days after exposure. The mice were also tested in the temperature gradient at 1, 5, and 12 days after exposure. The BTX-treated mice underwent an increase in Tc when placed in the temperature gradient but SFT was unaffected. This effect developed by 5 days and persisted at 12 days after exposure. This suggests an unusual delayed effect of BTX, characterized by an exacerbated stress-induced hyperthermia from being placed in a novel environment (i.e., temperature gradient). Overall, acute BTX exposure leads to a regulated reduction in Tc as characterized by a preference for cooler SFT's and a reduced Tc. Thermal dysthesia was not apparent; however, the exaggerated hyperthermic response with a normal SFT in the gradient may suggest an altered processing of thermal stimuli in mice treated with BTX. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.