Effects of chronic intermittent cold stress on pituitary adrenocortical and sympathetic adrenomedullary functioning.
Basal and stress-induced pituitary-adrenocortical (PA) and sympathetic adrenomedullary (SAM) function was investigated in rats exposed to chronic intermittent cold stress (4 degrees C for 4 h a day for 21 days; CHR). We found that basal plasma levels of corticosterone (B), corticosteroid-binding-globulin, ACTH, epinephrine (E) and norepinephrine (NE) were similar in CHR and control (CTL) animals. In contrast, activity of the adrenal catecholamine-synthesizing enzyme tyrosine hydroxylase, but not phenylethanolamine-N-methyl transferase, was significantly elevated in CHR compared to CTL. Following exposure to a heterotypic stressor (20 min restraint), plasma levels of B were significantly higher in CHR than CTL, but the stress-induced levels of E and NE were not different between groups. These data suggest that, although basal PA function is not altered by exposure to chronic intermittent cold stress, components of the SAM system are affected by this paradigm, and that co-ordinate facilitation of both PA and SAM responses to a novel stressor is not a necessary consequence of exposure to chronic intermittent stress.