  We present measurements of the dark matter bispectrum in N-body simulations
with non-Gaussian initial conditions of the local kind for a large variety of
triangular configurations and compare them with predictions from Eulerian
Perturbation Theory up to one-loop corrections. We find that the effects of
primordial non-Gaussianity at large scales, when compared to Perturbation
Theory, are well described by the initial component of the matter bispectrum,
linearly extrapolated at the redshift of interest. In addition, we find that,
for f_NL=100, the nonlinear corrections due to non-Gaussian initial conditions
are of the order of ~3, 4% for generic triangles up to ~20% for squeezed
configurations, at any redshift. We show that the predictions of Perturbation
Theory at tree-level fail to describe the simulation results at redshift z=0
already at scales corresponding to k ~ 0.02 - 0.08 h/Mpc, depending on the
triangle, while one-loop corrections can significantly extend their validity to
smaller scales. At higher redshift, one-loop Perturbation Theory provides
indeed quite accurate predictions, particularly with respect to the relative
correction due to primordial non-Gaussianity.
