  We reanalyse the production of $p\bar{p}$ pairs in proton-nucleus and
nucleus-nucleus collisions employing novel elementary cross sections for
baryon-baryon and pion-baryon production channels based on a boson-exchange
model. In contrast to previous transport studies performed in the literature
the secondary pion induced channel is found to be most important in both p+A
and A+A collisions at subthreshold energies. A detailed comparison with the
experimental data available indicates that sizeable attractive $\bar{p}$
potentials in the order of - 100 to - 150 MeV at normal nuclear matter density
are needed to reproduce the size and shape of the experimental spectra.
