The Journal of Neuroscience, May 1, 2003, 23(9):3924
Brain Hyperthermia Is Induced by Methamphetamine and Exacerbated
by Social Interaction
P. Leon
Brown,
Roy A.
Wise, and
Eugene A.
Kiyatkin
Behavioral Neuroscience Branch, National Institute on Drug Abuse,
Intramural Research Program, Baltimore, Maryland 21224
Hyperthermia is a symptom of methamphetamine (METH) intoxication
and a factor implicated in neurotoxicity during chronic METH use. To
characterize the thermic response to METH, it was injected once daily
into rats at increasing doses (0, 1, 3, and 9 mg/kg, s.c.) while brain
[nucleus accumbens (NAcc), hippocampus] and body (deep temporal
muscle) temperatures were continuously monitored. METH produced
dose-dependent hyperthermia, with brain structures (especially the
NAcc) showing a more rapid and pronounced temperature increase than the
muscle. At the highest dose, brain and body temperatures increased
3.5-4.0°C above basal levels and remained elevated for 3-5 hr.
Stressful and other high-activity situations such as interaction with a
conspecific female are also known to induce a significant hyperthermic
response in the rat. A combination of social interaction and METH
administration was tested for additive effects. Male rats were exposed
daily to a conspecific female for a total of 120 min, and METH was
injected at the same doses 30 min after the initial contact with the
female. An initial hyperthermic response (~1.5°C) to social
interaction was followed by a large and prolonged hyperthermic response
(3.5-5.0°C, 5-7 hr at 9 mg/kg) to METH, which was again stronger in
brain structures (especially in the NAcc) than in the muscle. Although
the combined effect of the hyperthermic events was not additive, METH
administration during social interaction produced stronger and
longer-lasting increases in brain and body temperature than that
induced by drug alone, heating the brain in some animals near its
biological limit (>41°C).
Key words:
brain temperature; hyperthermia; metabolic neural
activation; nucleus accumbens; hippocampus; social interaction
Copyright © 2003 Society for Neuroscience 0270-6474/03/2393924-06$05.00/0