  We explore an effective 4D cosmological model for the universe where the
variable cosmological constant governs its evolution and the pressure remains
negative along all the expansion. This model is introduced from a 5D vacuum
state where the (space-like) extra coordinate is considered as noncompact. The
expansion is produced by the inflaton field, which is considered as
nonminimally coupled to gravity. We conclude from experiental data that the
coupling of the inflaton with gravity should be weak, but variable in different
epochs of the evolution of the universe.
