Fig. 7. Inhibition of MAP kinase activation prevents gap junction closure, but does not inhibit nuclear envelope breakdown in response to LH. (A) U0126 (10 µm) inhibits LH-stimulated gap junction closure. Alexa Fluor 350 was injected at 72 minutes after applying LH, and the follicle was imaged 20 minutes later. (B) Ratio of fluorescence intensity in the mural granulosa cells to that in the inner cumulus cells, comparing follicles that had been treated with LH for 1 hour (66-72 minutes) in the presence of 10 µm U0126, and follicles without LH treatment (data from Fig. 1F). Measurements were made at 20 minutes after injecting Alexa Fluor 350 into the oocyte. Bars show mean±s.e.m. (C) A concentration of 100 µm U0126 inhibits LH-stimulated NEBD, but 10 µm U0126 does not. For B and C, n is the number of follicles tested for each condition.