Effects of weaning on expression levels of pituitary-derived FSH regulating factors. Levels of pituitary Fst (A), Fst isoform 288 (labeled Fst-288)(B), Adcyap1 (C), and Inhbb (D) mRNAs were determined by RT-PCR. Data are expressed as mRNA expression levels relative to Day 17 values. Each value represents the mean ± SEM of 6 animals. *, significantly different (P < 0.05) from Day 17 values within groups; δ, significantly different (P < 0.05) from control values on the same day.