Effect of treatment with estradiol benzoate on CL apoptosis and weight in the rat ovary after parturition. Ovaries were obtained at 13:00 hon day 4 post-partum from animals that had received vehicle (V) [non-lactating animals treated daily with sunflower seed oil at 10:00 h (n = 6–8)], or estradiol benzoate (EB) [non-lactating animals treated daily with estradiol benzoate (5 μg/rat s.c.) at 1000 h (n = 6–8)]. The ovaries were processed for routine H&E staining, and the number of apoptotic figures was counted under a light microscope (A and B). The average weight of the CL was recorded in two other groups of 6 to 8 animals (C and D). Filled bars represent old CL of gestation, whereas open bars represent newly formed CL after ovulation post-partum. *** p < 0.001 compared with vehicle (Student t-test).