A behavioural model, accompanied by biochemical analysis, was used to study the effects of the GABA-A receptor agonist muscimol on untreated and ethanolamine O- sulphate (EOS)-treated male rats. The most pronounced effect of muscimol was a lengthening of the duration of investigating behaviour. Pretreatment with EOS for 29 days potentiated this effect. Muscimol decreased the accumulation of GABA in the substantia nigra after 8 days but not after 30 days of EOS treatment, indicating that receptor adaptation might have occurred. We conclude that muscimol influences investigating behaviour and that chronic elevated brain GABA levels potentiate this effect.
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