PROLONGED STRESS-INDUCED ELEVATION IN PLASMA-CORTICOSTERONE DURING PREGNANCY IN THE RAT - IMPLICATIONS FOR PRENATAL STRESS STUDIES

Experiments were conducted to test the hypothesis that exposure to unc ontrollable stress during pregnancy results in a heightened elevation of plasma glucocorticoids. Rats were exposed to uncontrollable electri c tail shocks every other day during the 3 weeks of pregnancy. Plasma corticosterone concentrations in stressed darns increased significantl y from gestation days 4 to 20. Importantly, this increase in plasma co rticosterone occurred 24- and 48-h after exposure to stress suggesting a prolonged elevation in stress-induced glucocorticoid secretion. In addition, the stress-induced rise in plasma corticosterone was accompa nied by a significant decrease in maternal levels of corticosteroid bi nding globulin which suggests increased circulating levels of free cor ticosterone. Significant stress-induced elevations in plasma corticost erone also occurred in Fetuses that were examined on gestation day 20. Furthermore, a significant positive correlation was found between mat ernal and Fetal plasma corticosterone. Results demonstrate that repeat ed exposure to uncontrollable stress increases plasma concentrations o f glucocorticoids throughout pregnancy. In the unbound state, corticos terone may be highly effective in producing alterations in brain devel opment of offspring. These data have important implications for unders tanding the process underlying the effects of prenatal stress. (C) 199 8 Elsevier Science Ltd. All rights reserved.