Dopamine receptor gene expression in an animal model of 'behavioral dependence' on ethanol.
The steady-state levels of messenger RNA (mRNA) of five cloned dopamine (D) receptors were measured in five brain regions in rats in a recently developed animal model of 'behavioral dependence' on ethanol. One group of rats was given the choice between ethanol and water over a 9-month period and developed 'behavioral dependence' on ethanol (group a). This group was compared with a group given the choice between ethanol and water for only 2 months (not yet behaviorally dependent, group b), a group forced to consume ethanol as sole fluid over a 9-month period (not behaviorally dependent, group c) and ethanol-naive control rats. All groups were sacrificed 1 month after ethanol withdrawal. The concentrations of mRNA of D3-receptors in the limbic forebrain (which included the nucleus accumbens) were significantly lowered in groups a and b, but unchanged in group c. D3 mRNA levels were reduced in the hippocampus of group b and unchanged in the cortex, amygdala and striatum. No significant changes in the mRNA concentrations of D1-, D2-, D4- or D5-receptors were seen in the five brain regions in any group. In conclusion, chronic consumption of ethanol under the 'free-choice condition', which may best induce the drug-rewarding effect, leads to specific changes in the D3-receptor gene expression which were not seen after forced ethanol administration. Changes in D3 mRNA levels were, however, not a specific correlate of 'behavioral dependence', as they were also detected in rats not yet 'behaviorally dependent' (group b).
Eravci
M
M
Department of Radiological Diagnostics and Nuclear Medicine, Klinikum Benjamin Franklin, Free University of Berlin, Germany.
Grosspietsch
T
T
Pinna
G
G
Schulz
O
O
Kley
S
S
Bachmann
M
M
Wolffgramm
J
J
Götz
E
E
Heyne
A
A
Meinhold
H
H
Baumgartner
A
A
D000428:Alcohol Drinking; D000437:Alcoholism / Q000378:metabolism*; D000818:Animals; D002755:Choice Behavior / Q000502:physiology*; D004195:Disease Models, Animal; D005786:Gene Expression Regulation / Q000187:drug effects*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D011954:Receptors, Dopamine / Q000235:genetics*
D011954:Receptors, Dopamine