Effects of learned helplessness on brain GABA receptors

GABA is involved in both clinical depression and in animal models of depres sion; however, the roles of GABA(A) and GABA(B) receptors in specific brain regions are not clear. Changes in densities of both GABA(A) and GABA(B) re ceptors have been reported with the learned helplessness animal model of de pression and with chronic antidepressant drug treatment. However, some of t hese findings are discrepant. Thus, we used quantitative autoradiography to study the GABA(A) and GABA(B) receptors in learned helplessness and we use d an experimental paradigm that allows non-specific effects of stress to be differentiated from learned helplessness. Densities of GABA binding were m easured in prefrontal cortex, septum, hippocampus, hypothalamus and amygdal a. In the septum, learned helpless rats had increased densities of GABA(A) receptors and rats that did not become helpless after inescapable stress ha d decreased GABA(B) receptor densities. No significant group differences of GABA(A) or GABA(B), receptor densities were observed in any other brain re gion studied. These results suggest a unique role for the septum in modulat ing GABA in the learned helplessness animal model of depression. (C) 2000 P ublished by Elsevier Science Ireland Ltd and the Japan Neuroscience Society .