Number of oocytes (mean ± SEM) recovered from the oviducts of WT and nNOS−/− females following gonadotropin-stimulated ovulation. Each oviduct was separated from the ovary and uterine horn. Oocytes were counted under a dissecting microscope (×40) after the hyaluronidase had removed all cumulus cells. nNOS−/− females have fewer oocytes present in their oviducts than WT females following gonadotropin stimulation. Asterisk indicates p < 0.05; bars indicate SEM.