Effects of adrenocortical stress responses and metabolic functions during and after long-term administration of dexamethasone to adult Evans-Long rats.

During the last 75 days of a 130-day period of daily ip. administration of dexamethasone (DEX) sodium phosphate to adult female Evans-Long rats, mean body weight stabilized 20% below that of the controls, returning to the comparison-control level by the 64th day after the end of DEX treatment. Throughout the experiment, all animals received Purina Laboratory Chow, tap water, and a 0.7 M NaCl solution ad libitum. With DEX dosage, daily total fluid intake means determined weekly were consistently greater than the control values. There were 11 instances of increased saline intake also accompanied by significant increases in daily total fluid intake, but these did not establish salt dependency. Plasma corticosterone levels during DEX treatment were decreased significantly, but the DEX group was still responsive to stress; a significant within-subjects correlation, seen only in this group, between low- and high-stress corticosterone levels suggests that DEX selectively suppressed stress-release factors. Mean corticosterone levels of the DEX group sampled under conditions of increased stress did not exceed those for low-stress sampling of the controls. Following a recovery period after termination of DEX dosage, corticosterone levels were the same for both groups sampled under similar stress conditions and were not correlated with stress levels or with adrenal weights in either group.