  The Bjorken-Johnson-Low theorem applied to the $\gamma^\ast \to \gamma^\ast
\pi^0$ process provides us with a rather remarkable asymptotic behaviour for
the $\pi^0 \gamma^\ast \gamma^\ast$ vertex. We compare our result with previous
QCD- inspired estimates and argue that the predicted behaviour is quite
consistent with the present data on hadronic $J/\Psi$ decays and ensures the
matching of long- and short-distance radiative corrections to $\pi^+ \to e^+
\nu_e$.
