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0007-4888/03/13660563$25.00 © 2003 Plenum Publishing Corporation
Effect of Chronic Caffeine Consumption on Changes
in Locomotor Activity of WAG/G and Fischer-344
Rats Induced by Nicotine, Ethanol, and Morphine
S. K. Sudakov, I. V. Rusakova, and O. F. Medvedeva
Translated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 136, No. 12, pp. 638-640, December, 2003
Original article submitted August 28, 2003
We studied the effect of single treatment with nicotine, ethanol, and morphine on locomotor
activity of WAG/G and Fischer-344 rats chronically drinking caffeine solution. In Fischer-
344 rats receiving caffeine locomotor activity in the open-field test was much lower than in
animals drinking water, while in WAG/G rats no differences in locomotor activity were found.
Chronic caffeine intake increased rat sensitivity to the stimulating effect of nicotine and
ethanol, but decreased their sensitivity to the depressant effect of morphine. Chronic caffeine
treatment most significantly modulated the effects of nicotine, ethanol, and morphine in
Fischer-344 rats.
Key Words: rats; locomotor activity; caffeine; nicotine; ethanol; morphine
National Research Center for Narcology, Russian Ministry of Health;
Institute of Human Morphology, Russian Academy of Medical Sci
ences, Moscow.
Address for correspondence:Address for correspondence:
Address for correspondence:Address for correspondence:
Address for correspondence: ssudakov@mtunet.ru.
Sudakov S. K.
Caffeine is widely consumed by humans. Coffee, tea,
cacao, and cold drinks contain a considerable amount
of this psychoactive substance. Civilized people con-
sume caffeine in a daily dose of 3.0 mg/kg primarily
with coffee [6]. Single administration of caffeine pos-
sessing psychopharmacological activity produces psy-
chostimulant, anxiogenic, and other effects [7,9,12].
Chronic consumption of caffeine also has a psycho-
tropic effect [4]. Acute and chronic administration of
caffeine modulates the effects of other psychoactive
substances, including amphetamine [10], cocaine [11],
and morphine [8]. Caffeine increases positive rein-
forcement properties of alcohol and nicotine. The pro-
ducts containing these substances are often consumed
together with each other (triple “c”: coffee, cognac,
and cigar). The influence of chronic caffeine con-
sumption on the sensitivity to acute effects of psycho-
active substances consumed by people is poorly
studied.
Here we studied the effect of single treatment
with nicotine, ethanol, and morphine on locomotor
activity of rats chronically receiving caffeine with
drinking water. Our previous studies showed that
WAG/G and Fischer-344 rats differ in their sensitivity
to acute and chronic effects of caffeine [2,4].
MATERIALS AND METHODS
Experiments were performed on male WAG (n=64)
and Fischer-344 rats (n=64) weighing 180-200 g. Be-
fore the experiment the animals were housed in cages
(8 rats per cage) and had free access to standard feed
and drinking water. The light/dark period was 12:12 h
(daytime 9.00-12.00).
The rats were divided into 2 groups (32 animals
of each strain). Some rats received 0.1% caffeine solu-
tion instead of drinking water for 30 days. Other rats
drank water in this period.
On day 30 the animals were placed in a square
open field (50×50 cm). Locomotor activity was recor-
ded automatically with infrared sensors fixed in walls
of the open field. Control (n=8) and experimental ani-
mals (n=8) of each strain were injected with nicotine
Bulletin of Experimental Biology and Medicine, No. 6, 2003 PHARMACOLOGY AND TOXICOLOGY