Reduced expression of GABA transporter GAT3 in helpless rats, an animal model of depression

Mood disorders have been linked to glial and synaptic pathology such as disturbed neurotransmission of gamma-aminobutyric acid (GABA). We evaluated the expression of GABAergic marker genes in rats with helpless behaviour, an animal model of depression. Male Sprague-Dawley rats from inbred lines were tested for helpless behaviour and grouped according to failures in terminating foot shock currents. Expression levels of GABAergic marker genes were assessed using semiquantitative in situ-hybridization. Animals with congenital helpless behaviour (cH) were unable to escape current exposure in contrast to cH-animals derived from the same litters with low failure rates and to non-helpless animals (cNH). We found a significant downregulation of the GABA transporter GAT3 in cLH rats. GAT1 showed small changes, glutamic acid decarboxylase (GAD67) and the vesicular GABA transporter were not significantly altered. Reduced GABA transporter expression is well in concert with the behavioural phenotypes of knockout animals and strengthens the hypothesis of impaired glial functions in depression.