Trace Elements Distribution in the Brain of Stressed Rats

Because of their ability to modulate the Gamma Aminobutyric Acid (GABA) a receptor complex, the principal aim of the current work is to assess two essential heavy metals: Iron (Fe) and zinc (Zn) by atomic absorption in different brain areas of stressed rat s. To do so, we investigated the effect of acute immobilization stress (single 1-hour session) on th e distribution and the densities of GABA A receptors as well as the concentrations of Zn and Fe in several rat brain regions of the stressed rats. Animals wer e randomly assigned to either control or stress condi tions and changes in specific binding of the GABA A receptor as labelled with T-Butylbicyclophosphonothionate (TBPS) (ligand useful for GABA A receptor) were assessed by in vitro quantitative autoradiogra phy with the aid of a computer-assisted image analy sis system whereas the assessment of Fe and Zn concentrations was done by atomic absorption spectrophotometry. Exposure to 1h immobilization stress led to a significant increase in [ 35 S]-TBPS binding site density in stressed rats compared to controls (30-40% increase in cortex, hypothalamus, hippocampus and substatntia nigra). In the other analyzed brain structures, specific binding of [ 35 S]-TBPS remained unchanged in stressed rats. The spectrophotometer a nalysis showed significant decrease in Zn levels in the whole forebrain structures as well as the mesenceph alon of stressed rats. The striking differences are noticed in hippocampus and mesencephalon. Furthermore, Fe endogenous concentrations display similar pattern following stress. The present study demonst rates that immobilization stress induces an increas e in GABA A receptors concomitant to a reduction of Zn and Fe c ontent in the stress sensitive rat brain structures . Besides supporting the alteration of the modulatory function occurring at the GABA A receptor level after stress, our data also reveal that the measured brai n concentrations of the investigated heavy metals r emain not sufficient to efficiently modulate the activity of with efficacy such complex receptor. This could explain the higher densities of GABA A receptors observed after acute stress.