  The one-loop electroweak radiative corrections to coherent forward neutrino
scattering in a medium slightly violates the tree-level universality of
neutral-current contributions of three neutrino flavors to the matter potential
that is relevant to neutrino oscillations in matter. We examine this small but
nontrivial quantum effect by deriving the differential equations of those
effective neutrino oscillation quantities with respect to the electron number
density of matter. The tree-level Toshev relation $\sin 2\tilde{\theta}_{23}
\sin\tilde{\delta} = \sin 2\theta_{23} \sin\delta$, which links the fundamental
flavor-mixing and CP-violating parameters
