Gene expression of receptors and enzymes involved in GABAergic and glutamatergic neurotransmission in the CNS of rats behaviourally dependent on ethanol

1 The steady state levels of the messenger RNA (mRNA) of eight GABA, recept or subunits, five glutamate receptor subunits and seven enzymes involved in the synthesis of glutamate and GABA were measured in eight regions of rat brain in a recently developed animal model of 'behavioural dependence' on e thanol. 2 'Behavioural dependence' including loss of control was induced by offerin g the rats the choice between ethanol and water over a 9-month period (Grou p A). This group was compared with a group given the choice between ethanol and water for only 2 months (not yet 'behaviourally dependent', Group B), a group forced to consume ethanol as sole fluid over a 9-month period (also not 'behaviourally dependent', Group C) and ethanol-naive control rats (Gr oup D). All groups were sacrificed 1 month after the ethanol was withdrawn. 3 The mRNA concentrations of all eight GABA receptor subunits, four out of the five subunits of different glutamate receptors and those of seven enzym es involved in GABA and glutamate Production were reduced almost exclusivel y in the parieto-occipital cortex in Groups A and B, but not Group C. 4 These data suggest that the synthesis of glutamate and GABA and the activ ities of their respective neurons are selectively impaired in the parieto-o ccipital cortex in the groups having consumed ethanol in a free-choice desi gn, in which its rewarding properties can better take effect than after for ced administration. 5 As the parieto-occipital cortex is believed to contain emotional memory s tructures, it may be hypothesized that the glutamatergic and GABAergic neur onal systems in this area are involved in the development of memory for rew ard from ethanol. However, they are not specifically associated with 'behav ioural dependence'.