Dissociation of oocyte maturation and ovulation in mice pretreated with a derivative of dihydropyridazinone.

Treatment of mice with a dihydropyridazinone derivative (6-(4'-aminophenyl)-4,5-dihydro-5-methylpyridazin-3-one; ICI 109,081) inhibited the maturation of oocytes in the presence of gonadotrophins without affecting ovulation. The spontaneous resumption of meiosis in oocytes cultured in vitro was reversibly inhibited. ICI 109,081 may therefore be useful for evaluating the relationship between follicular development and the resumption of meiosis.