FIGURE 6. Effect of removal of progesterone’s influence on intensity of 
c-Fos protein in activated LHRH neurons. In addition to 
reducing the number of neurons activated during an LH surge, 
ovariectomized rats replaced with estrogen only showed a 
marked reduction in the intensity of c-Fos staining in LHRH 
neurons. (A) Ovariectomized rat treated with estrogen and 
progesterone; (B) ovariectomized rat treated only with estrogen. 
Similar results were obtained following treatment of intact cycling 
rats with RU 486. 
SOURCE: Lee etal. 1990a 
126 
