Effect of stress on the behavior and 5-HT system in Sprague-Dawley and Wistar Kyoto rat strains.

The effects of chronic novel stressors, for 21 days, on the behavior and the serotoninergic (5-HT) system in Sprague-Dawley (SD) and Wistar Kyoto (WKY) rats were studied. Open-field and forced-swim tests revealed a significantly greater behavioral depression in the WKY strain. SD rats showed a decrease in 3H-DPAT binding to 5-HT1A receptors in the hippocampus, whereas WKY rats revealed an increase in 3H-DPAT binding in the hippocampus and hypothalamus. Stress did not appear to alter the binding of 3H-DPAT to 5-HT1A sites in the dorsal raphe or median raphe in either strains. SD rats revealed a modest increase in 5-HT transporter (5-HTT) sites in the cortex; WKY rats revealed a decrease in 5-HTT sites in the cortex and the hippocampus. Stress caused an increase in 3H-CNIMI binding to 5-HTT sites in the dorsal and median raphe nuclei in both strains. The results suggest that the greater susceptibility to behavioral depression in WKY rats may account for the differential effects on 5HT1A sites as well as 5-HTT sites in limbic regions and cell body area as compared to SD rats.