Acute and delayed thermoregulatory response of mice exposed to brevetoxin

Thermal dysthesia, characterized by a painful sensation of warm and cool su rfaces, is one of many ailments in humans exposed to various marine algal t oxins such as brevetoxin (PbTx). There is no animal model to study thermal dysthesia and little is known of the mechanism of action. There is also lit tle known on the acute and delayed thermoregulatory effects of PbTx. In thi s study, we developed a behavioral system to assess the possible developmen t of thermal dysthesia in mice exposed to PbTx. Female mice were implanted with radiotransmitters to monitor core temperature (T-c) and motor activity (MA). In one experiment, mice were dosed with the control vehicle or 180 m ug/kg PbTx and placed on a floor temperature gradient to measure the select ed foot temperature (SFT) while air temperature was kept constant. PbTx-tre ated mice underwent a 10 degreesC reduction in SFT concomitant with a 3 deg reesC reduction in T-c within 30 min after exposure. In another study, T-c and MA were monitored in mice maintained in their home cages after dosing w ith 180 mug/kg PbTx. T-c but not MA increased for 2-5 days after exposure. SFT was unaffected by PbTx when tested 1-12 days after exposure. However, P bTx-treated mice underwent an increase in T-c when placed in the temperatur e gradient for up to 12 days after exposure. This suggests that PbTx augmen ts the stress-induced hyperthermia from being placed in a novel environment . Overall, acute PbTx exposure leads to a regulated reduction in T-c as cha racterized by a preference for cooler SFTs and a reduced T-c. Thermal dysth esia was not apparent, but the exaggerated hyperthermic response with a nor mal SFT in the temperature gradient may suggest an altered processing of th ermal stimuli in mice treated with PbTx. (C) 2001 Elsevier Science Ltd. All rights reserved.