Study on Injuries to Hippocampus, Amygdala, Cerebral Cortex and Their Effects on Conditioned Taste Aversion in Total Body

The objective was to study the effects of one time exposure to small clinically relevant dose of 60 cobaltgamma ( 60 Co-γ) radiation on histological changes in brain and consequent effects on conditioned taste aversion (CTA) in experimental rats. Rats were total body 60 Co-γ-irradiated in GammaCell; CTA to saccharin was assessed in terms of saccharin preference ratio (SPR) using a standardized two bottle regime; brain histology was performed as per standard procedures. Total body exposure to 60 Co-γ-irradiation (2Gy) caused nuclear degeneration, increase in intercellular spaces, enucleation in amygdala as well as in cerebral cortex, neuronal loss and dispersion of neurons in hippocampus at 24 h after irradiation. Most of the cellular and nuclear damage in these brain parts had shown increasing trend up to day 5. In irradiated animals, maximum CTA acquisition {25.6±3.6% SPR [t(6)=3.499, p<0.05]} was at 24 h (day1) after irradiation, which did not change from day1 till day 5(F4, 4=2.772, p=0.1736). This study suggested that whole body exposure to rats at clinically relevant dose of 60 Co-γ-ray caused lesions in cerebral cortex, hippocampus and amygdala, which did not prevent acquisition of CTA. Further, post-irradiation time dependent histological changes in these brain parts did not influence the retention of CTA.