Abstract
Objective: To study the effects of chronic restraint stress on body weight with respect to serum corticosterone levels in Sprague Dawley rats.
Methodology: This experimental study was carried out at Department of Physiology, Army Medical College, Rawalpindi & NIH Islamabad, Pakistan from January 2008 to December 2008. Out of a total of 150 rats, 90 were female and 60 were male.They were divided into five groups; Group I and II were control groups where as III, IVa, IVb were experimental groups. The control male rats were exposed to chronic restraint stress where as the experimental female rats were exposed to the similar stress regimen. Later they had removal of both ovaries. Half of the ovariectomized rats (n=30) were given once daily injection of 17- β estradiol for two weeks. The body weights of the male and female Sprague Dawley rats were recorded both at the start and end of study.
Results: The stress resulted in an increase in serum corticosterone levels in experimental male rats (21.66±3.67 ng/ml, p<0.05) as compared to control male rats (16.16±5.66 ng/ ml, p<0.05). Similar stress regimen resulted in a significant increase in serum corticosterone levels of estradiol treated female rats (31.32±5.46 ng/ml, p<0.05) as compared to healthy controls (17.48±4.14 ng/ml). The body weights of the experimental rats exposed to chronic restraint stress were significantly increased (298.87±8.78 gm, p< 0.05) at the end of study as compared to start of study (280.53±3.64gm, p=0.05). The body weights of OVX vehicle treated rats were significantly increased at the end of study (269.47±4.51 gm, p<0.001) as compared to estradiol treated OVX rats at the end of study (256.90±4.63gm, p<0.001).
Conclusion: Chronic restraint stress resulted in increase in serum corticosterone levels and body weight both in male and female Sprague Dawley rats.

Key words: Hypothalamo pituitary adrenal(HPA) axis, Stress, Corticosterone, Restraint, Body weight, Ovariectomy, Estradiol