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.