The Journal of Neuroscience, December 1, 2002, 22(23):10487-10493
Low Ethanol Sensitivity and Increased Ethanol Consumption in Mice
Lacking Adenosine A2A Receptors
Mickaël
Naassila1,
Catherine
Ledent2, and
Martine
Daoust1
1 Laboratoire de Physiologie-Alcoologie,
Université de Picardie Jules Verne, Faculté de Pharmacie,
80000 Amiens, France, and 2 Institut de Recherche
Interdisciplinaire, Université Libre de Bruxelles, B-1070
Brussels, Belgium
We have shown previously that the severity of handling-induced
convulsions during ethanol withdrawal was reduced in A2A
receptor knock-out (A2AR
/
)
mice. In the present report, we further characterize the role of
adenosine A2A receptors in ethanol consumption and
neurobiological responses to this drug of abuse. Male
A2AR
/
mice showed increased
consumption of solutions containing 6 and 20% (v/v) ethanol compared
with wild-type (A2AR+/+) control mice;
female A2AR
/
mice showed increased
consumption of solutions containing 6 and 10% ethanol. This slightly
higher ethanol consumption was also related to increased ethanol
preference. In contrast, A2AR
/
mice
showed normal consumption of solutions containing either sucrose or
quinine. Relative to A2AR+/+ mice,
A2AR
/
mice were found to be less
sensitive to the sedative effect of 3.0 gm/kg ethanol, as measured by
more rapid recovery from ethanol-induced loss of righting reflex, and
to the hypothermic effects of 1.5, 3.0, and 4.0 gm/kg ethanol, although
plasma ethanol levels did not differ significantly between the two
genotypes. The selective adenosine A2A receptor antagonist
ZM 241385 (4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol) (10-30 mg/kg) significantly attenuated ethanol-induced (4.0 gm/kg) hypothermia in CD1 mice. To assess whether ethanol administration would
induce differential tolerance in
A2AR
/
and wild-type mice, we
administered ethanol (3.0 gm/kg) over 4 consecutive days and found no
difference in the development of tolerance; however, female
A2AR
/
mice showed a lower
tolerance-acquisition rate. These data suggest that activating the
A2A receptors may play a role in suppressing alcohol-drinking behavior and is associated with the sensitivity to the
intoxicating effects of acute ethanol administration.
Key words:
adenosine; A2A receptor; ethanol; hypothermia; knock-out mice; sensitivity; tolerance; ZM 241385
Copyright © 2002 Society for Neuroscience 0270-6474/02/222310487-07$05.00/0