Fig. 1. Representative northern blot of brain-derived neurotrophic factor (BDNF) mRNA in theca cells (A) reveals two transcripts of approximately 4.5kb and 1.5kb. Levels of mRNA were measured by densitometric scans of northern blots and were standardized to 18S rRNA (B). Data are expressed as fold difference compared with F1 follicle theca. Values are means + S.E.M. (N=3 replicate experiments). a and b denote significant differences (P<0.05) in levels of the 4.5kb transcript. Str, stromal tissue; 3–5 and 6–8 refer to the diameter (in mm) of prehierarchal follicles, while 9–12 (follicle diameter 9–12mm) and F3, F2 and F1 represent preovulatory follicles, with F1 representing the next follicle to ovulate.