Effect of the GABA-transaminase inhibitor vigabatrin on exploratory behaviour in socially isolated rats.

Elevation of the brain levels of the major inhibitory neurotransmitter gamma-aminobutyric acid (GABA) by inhibiting the GABA-catabolizing enzyme GABA-transaminase (GABA-T) is known to induce a number of functional effects including changes in behaviour. Vigabatrin (gamma-vinyl GABA, GVG) is an anti-epileptic drug that increases brain GABA levels by an irreversible inhibition of GABA-T. Using the elevated plus-maze model of anxiety and the open-field behaviour test, the effects of GABA-T inhibition and social isolation on rat exploratory behaviour were investigated. Social isolation for 1 week did not induce any change in the exploratory-behaviour of adult rats. However, rats socially isolated for 2 weeks, showed suppressed exploratory behaviour in the elevated plus-maze test. In both groups of differentially housed rats, treatment with vigabatrin at a dose of 250 mg/kg, i.p., significantly reduced the anxiety level in the plus-maze test. In the open-field test, vigabatrin tended to increase the exploratory behaviour only in the group of isolated rats. The results may suggest that vigabatrin has a better anxiolytic-like effect in the isolated rats than that in the socially housed rats.