Coping in an intermittent swim stress paradigm compromises natural killer cell activity in rats.

The effects of intermittent swim stress and stressor controllability on natural killer cell activity (NKCA) was examined. Significant decreases in splenic NKCA were observed immediately post-stress, but only when the stress was controllable. Although decreased NKCA was also observed in yoked rats subjected to the same stressor, it failed to attain statistical significance. Previous results suggest these effects are not due to corticosterone. The results suggest a cost of coping on the acute, in vitro immune measure of NKCA.

Endocrine and immunological correlates of behaviorally identified swim stress resilient and vulnerable rats.

Animal models of stress-induced depression have identified a bimodal reactivity to stress, namely 'resilience' and 'vulnerability.' Possible corresponding differences in endocrine and immunological responses between these groups have not been delineated. Male Sprague-Dawley rats were divided into three groups: stress (n=25), confined controls (n=7), and home cage controls (n=7). Stress rats were exposed to 80, 5-s inescapable cold water swim trials (15 degrees C). Twenty-four hours later, the stress rats were tested on an instrumental swim escape test (SET) but now they had access to an omnidirectional lever that terminated the stress. Immediately after the SET, trunk blood was collected to assay for serum corticosterone (CORT), and spleens were removed and natural killer cell activity (NKCA) and concanavalin A (CON-A) induced lymphocyte proliferation determined. Subjects in the stress treatment group were divided into distinct 'resilient' and 'vulnerable' categories by a median split for average escape latencies across the last 25 trials of the SET. Stress rats secreted more CORT than controls and vulnerable rats secreted greater levels than resilient rats. NKCA was greatest in control rats, and was decreased in the stress rats although the resilient and the vulnerable groups did not differ. Conversely, CON-A-induced lymphocyte proliferation was greatest in stress rats, vulnerable rats exhibiting more proliferation than resilient rats, but both were greater than both control groups. Stress animals were hypothermic throughout the swim stress procedures but exhibited a stress-induced fever following the initial swim trials. The observed differences may have important predictive and theoretical utility for vulnerable and resilient profiles.