In situ hybridization of BMPR-II mRNA in ovaries of adult cycling rats. Brightfield (A, C, D, F, H) and Darkfield (B, E, G). A, B: Sections from DI 1100 h ovaries (4X). Positive new CL-I; positive GC in GF, AF, and preantral follicles (arrow heads); negative secondary interstitial cells (SIC); C: Early secondary follicle showing positive GC surrounding weakly positive oocyte (40X); D, E: Dominant preovulatory follicle at E 0200 h (4X); positive MGC and negative oocyte (O) surrounded by weakly positive CC. F, G: Atretic follicle at P 2000 h (10X) showing positive GC. H: Higher magnification of new CL-I in panel A (40X); moderately positive lutein cells; negative endothelial cells (EC) and theca externa (TE).