ChAT is present in growing antral follicles of rat and monkey ovary. A-C: Rat ovaries: ChAT is not detectable using immunohistochemical methods in a rat ovary at postnatal days 0 or 6 (A, B). Bars = 50 μm. In adult rat ChAT (C) is present in GCs of antral follicles. Bar = 100 μm. D-F: Monkey ovaries: ChAT is not detectable using immunohistochemical methods in a monkey ovary at postnatal day 1 (D). The same ovary is shown after staining with H.E. to reveal structural details of follicle formation (E). Bars = 50 μm. F: Immunohistochemistry of an adult monkey ovary showing a large antral follicle (two asterisks) strongly stained for ChAT, preantral follicles (arrows) devoid of staining, and the appearance of immunoreactivity in follicles with incipient antrum formation (asterisk). Bar = 100 μm.