The Journal of Neuroscience, February 1, 2002, 22(3):1072-1080
Brain and Body Hyperthermia Associated with Heroin
Self-Administration in Rats
Eugene A.
Kiyatkin and
Roy A.
Wise
Behavioral Neuroscience Branch, National Institute on Drug
Abuse-Intramural Research Program, Baltimore, Maryland 21224
Intravenous heroin self-administration in trained rats was
accompanied by robust brain hyperthermia (+2.0-2.5°C); parallel changes were found in the dorsal and ventral striatum, mediodorsal thalamus, and deep temporal muscle. Temperature began to increase at
variable latency after a signal of drug availability, increased reliably (~0.4°C) before the first lever press for heroin,
increased further (~1.2°C) after the first heroin injection, and
rose more slowly after the second and third injections to stabilize at
an elevated plateau (39-40°C) for the remainder of the session.
Brain and body temperature declined slowly when drug
self-administration was terminated; naloxone precipitated a much more
rapid decrease to baseline levels. Changes in temperature were similar
across repeated daily sessions, except for the increase associated with the first self-administration of each session, which had progressively shorter latency and greater acceleration. Despite consistent biphasic fluctuations in movement activity associated with heroin
self-administrations (gradual increase preceding the lever press,
followed by an abrupt hypodynamia after drug infusion), mean brain
temperature was very stable at an elevated plateau. Only mean muscle
temperature showed evidence of biphasic fluctuations (±0.2°C) that
were time locked to and correlated with lever pressing and associated
movements. Drug- and behavior-related changes in brain temperature thus
appear to reflect some form of neuronal activation, and, because
temperature is a factor capable of affecting numerous neural functions,
it may be an important variable in the control of behavior by drugs of abuse.
Key words:
brain temperature; opiates; heroin; neural activation; drug-taking behavior; thermorecording in behaving animals
Copyright © 2002 Society for Neuroscience 0270-6474/02/2231072-09$05.00/0