Germinal vesicle breakdown (GVBD) is the hallmark of oocyte meiotic resumption. It occurs under minimal stimulation during in vitro maturation (IVM). Several factors have been described to be involved in the inhibition of oocyte meiotic resumption such as purine derivatives. This study was assessing whether adenosinergic and guanosinergic systems are functional and participating in the inhibition of oocyte maturation. The objectives of the present study were to evaluate the effect of two purines, adenosine (ADO) and guanosine (GUO), on in vitro oocyte meiotic resumption, cumulus cell expansion, and gap junction communication. Both ADO and GUO significantly inhibited GVBD oocytes. The inhibitory effect lasted 24 hours and was reversible for meiotic resumption and cumulus cell expansion. Both ADO and GUO increased gap junction communication in cumulus cells. Equine chorionic gonadotropin (eCG) and the adenylyl cyclase stimulator, forskolin (FK), were both supportive of ADO and GUO inhibitory effect. The results are suggesting both adenosinergic and guanosinergic systems efficient in inhibiting oocyte meiotic resumption. The use of these two systems as part of a pre- IVM culture period would be a novel strategy to explore in order to improve oocyte developmental competence.