REDUCED REPRODUCTIVE OUTCOME AND EXTENDED GESTATIONAL LENGTH IN PREGNANT RATS EXPOSED TO PREDATOR-INDUCED PSYCHOSOCIAL STRESS

Abstract

Maternal stress is commonly cited as a potential cause for idiopathic pregnancy loss. However, the mechanisms through which stress affects pregnancy are yet to be totally known. This study was designed to determine the effect of predator-induced psychosocial stress on implantation and pregnancy outcome in rat, as well as the hormonal changes associated with it. Cycling rats (n=60) in proestrus phase were paired overnight with sexually matured male in ratio 2:1. Following confirmation of mating in the morning, rats were randomly assigned to either control (n=30) or stress (n=30) group. Stress was induced by exposing rats to cat for 60 minutes/day for 14 consecutive days. Subsequently, six animals from each group were sacrificed on days 4 (embryo counting), 6, 8 (implantation studies), and 19 (for foetal parameters). Blood was collected through cardiac puncture for hormonal analysis andimplantation sites(IS) determined by injection of Evans blue dye. Remaining six animals in each group were allowed to deliver at term. Significant (p<0.05) reduction in number of implants was observed on days 6 and 8 compared with control while weight of ISwas reduced on day 8 compared with control. There wassignificant (p<0.05) reduction in the number and weight of foetuses and litters on day 19 and at term compared with their corresponding days in control. Corticosterone was elevatedin the stress groups compared with control. Progesterone-oestradiol ratio was significantly (p<0.05) lower in stress group compared with control on days 4 and 8.Also, length of gestation was significantly (p<0.05) extended in the stress group compared with control. This study suggests that exposure to predator-induced psychosocial stress reduced reproductive outcome and prolonged gestation length by interfering with the pituitary-adrenal and pituitary-ovarian axes.