To this aim, spermatozoa were cultured under conditions able to up or down regulate phospholipids disorder and sperm cholesterol efflux in the presence of Met-AEA or of the specific CB1R antagonist SR141716. The effects of the different treatments on the process of lipid remodelling were, then, evaluated by analyzing specific physic-chemical membrane parameters. In this study, the effect of CB1R activation on this crucial process of lipid sperm membrane reorganization was investigated, first by assessing how the CB1R distribution and activity change during the process of in vitro capacitation and then by describing the role exerted by the receptor on the physico-chemical proprieties of sperm membranes. The immunocytochemistry results showed that the incubation of spermatozoa under capacitating conditions caused a clear CB1R translocation from the post-acrosomal area to the equatorial region. The evolution of the different fluorescent patterns and the results obtained with the functional test of sperm exposure to ZP strongly MK-1775 Wee1 inhibitor indicated that capacitated spermatozoa displayed pattern B. Moreover, the functional correlation between cAMP-dependent signalling pathways and CB1R translocation to the equatorial district highlighted the inhibitory role of the receptor on the process of sperm capacitation. In fact spermatozoa maintained their uncapacitated status until CB1R activity was high and the receptor was localized in the post acrosomal region. Both these conditions were associated either with the presence of high levels of AEA when the receptor antagonist is absent or with the activity of other inhibitory molecules able to maintain low the intracellular cAMP levels. Under physiological conditions, the post-acrosomal distribution of CB1R is preserved until spermatozoa are exposed to high levels of extracellular AEA, as it occurs in seminal plasma and in the uterine district. Under these conditions, high levels of AEA may contribute to prevent a premature capacitation, by activating a CB1R-mediated reduction of intracellular cAMP. As the spermatozoa progress along the female genital tract, they are progressively exposed to lower concentration of AEA and higher of bicarbonate , thus the brake exerted by CB1R could be removed. At the same time, the receptor becomes BAY 73-4506 sequestrated in the equatorial region of the sperm , where it could be associated with reduced activity. In addition, an autocrine/paracrine inhibitory feedback exists between intracellular cAMP levels and CB1R localization. In fact, cAMP concentration may control the transition from pattern