Stress is a factor in psychopathological conditions including depression and anxiety. The brain noradrenergic system, associated with arousal and behavioral activation, is activated by stress. NE dysregulation may thus link stress to psychopathology. However, evidence suggests a genetic influence on stress susceptibility, so we compared noradrenergic stress reactivity in rat strains differing in their behavioral and physiological response to stress (Sands, SFN 1999). Wistar, Sprague-Dawley and Lewis rats show app 30% increase in tyrosine hydroxylase mRNA in locus coeruleus after acute restraint, but WKY rats show no increase. In this study, behavioral indices of stress reactivity indicate that WKY rats mainly exhibit behavioral inhibition in response to stress, consistent with a lack of noradrenergic reactivity. Compared to other rats, WKY show reduced locomotion, measured in an open field or as closed-arm entries in a plus maze (n=15-17, p<.05). Surprisingly, WKY rats spent a greater proportion of time in...