Endocrine Abstracts

Maternal stress is commonly cited as a potential cause for idiopathic pregnancy loss (Knackstedt et al., 2005). However, the mechanisms through which stress affects implantation and pregnancy are yet to be totally deciphered. This study was designed to determine the effect of predator-induced psychosocial stress on implantation and pregnancy in rat. Cycling rats (n=48) at proestrus phase were paired overnight with sexually experienced male in ratio 2:1. Following confirmation of mating in the morning, rats were registered to be on day one of pregnancy and randomly assigned to either control (n=24) or stress (n=24) group. Stress was induced by the method of Figueiredo et al., 2003; exposing rats to cat for 60 minutes/day for 14 consecutive days. Subsequently, six animals from each group were sacrificed by cervical dislocation on days 6, 8, and 19 and blood was collected through cardiac puncture for hormonal analysis. Remaining six animals in each group were allowed to deliver at term. Number, weight of implantation sites (IS) and litter size were determined as described by Iranloye et al., 2010. Results reveal significant (P<0.05) reduction in number and weight of IS on day 8 (6.40±0.72, 0.035±0.002 g) compared with control (10.83±0.48, 0.064±0.010 g). There is a significant (P<0.05) reduction in the number of fetuses and litters on day 19 (6.00±0.37) at term (6.17±1.01) compared with their corresponding days in control (9.00±0.37 and 9.83±0.54). Hormonal analysis reveal significant (P<0.05) elevation of corticosterone in the stress group (320.80±22.45; 423.30±35.28; 285.50±25.70) ng/ml compared with control (152.80±32.68; 170.20±38.63; 178.20±38.07) ng/ml, on days 6, 8, and 19. Prolactin concentration was significantly (P<0.05) reduced in stress group with control on days 6, 8 and 19. Gestation was also significantly (P<0.05) extended in the stress group. This study suggests that predator-induced psychosocial stress reduce implantation and pregnancy outcome as a result of stress-induced hormonal perturbation.