  Medium modifications of the $\pi \omega \rho$ vertex are analyzed in context
of the $\omega \to \pi^0 \gamma^\ast$ and $\rho \to \pi \gamma^\ast$ decays in
nuclear matter. A relativistic hadronic model with mesons, nucleons, and
$\Delta(1232)$ isobars is applied. A substantial increase of the widths for the
decays $\omega \to \pi^0 \gamma^\ast$ and $\rho \to \pi \gamma^\ast$ is found
for photon virtualities in the range $0.3-0.6$GeV. This enhancement has a
direct importance for the description of dilepton yields from dalitz decays in
relativistic heavy-ion collisions.
