GABA and glutamate overflow in the VTA and ventral pallidum of alcohol-preferring AA and alcohol-avoiding ANA rats after ethanol.
OBJECTIVE
Earlier findings suggest that dopaminergic neurons are probably not critically involved in ethanol self-administration behavior and in the differential intake of ethanol by the alcohol-preferring AA (Alko Alcohol) and non-preferring ANA (Alko Non-Alcohol) rat lines selected for differential ethanol intake. The purpose of the present study was, therefore, to clarify the role of GABAergic and glutamatergic afferents and efferents with the mesolimbic dopamine system in the control of ethanol intake as well as in differential intake of ethanol by AA and ANA rats.


METHODS
The effects of an acute dose of ethanol (1 or 2 g/kg i.p.) on the levels of GABA and glutamate in the ventral pallidum and the ventral tegmental area of AA and ANA rats were monitored with in vivo microdialysis. The concentrations of GABA and glutamate in the dialysates were determined with a high performance liquid chromatography system using fluorescent detection.


RESULTS
Ethanol significantly decreased the extracellular levels of GABA in the ventral pallidum but not in the ventral tegmental area. The ANA rats were more sensitive than the AA rats to the suppressive effect of ethanol on pallidal GABA levels. Ethanol did not have any effect on the concentrations of glutamate in either rat line.


CONCLUSIONS
The suppressive effect of ethanol on the extracellular levels of GABA in the ventral pallidum suggests a role for pallidal GABAergic transmission in the control of ethanol consumption.
Kemppainen
Heidi
H
Department of Drugs, Alcohol and Addiction, National Institute for Health and Welfare, POB 30, 00271 Helsinki, Finland.
Raivio
Noora
N
Nurmi
Harri
H
Kiianmaa
Kalervo
K
D000428:Alcohol Drinking / Q000235:genetics / Q000503:physiopathology*; D000435:Alcoholic Intoxication / Q000235:genetics / Q000503:physiopathology*; D000818:Animals; D001931:Brain Mapping; D002755:Choice Behavior / Q000502:physiology*; D000431:Ethanol / Q000097:blood; D005917:Globus Pallidus / Q000503:physiopathology*; D018698:Glutamic Acid / Q000378:metabolism*; D008297:Male; D017551:Microdialysis; D051381:Rats; D011919:Rats, Inbred Strains; D009435:Synaptic Transmission / Q000502:physiology; D017557:Ventral Tegmental Area / Q000503:physiopathology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D000431:Ethanol; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid