  The light-cone distribution amplitudes for the axial current are derived
within the instanton vacuum model (IVM), which incorporates nonperturbative
effects including spontaneous chiral symmetry breaking. This allows to extend
applicability of the dipole approach, usually used in the perturbative domain,
down to $Q^{2}\to0$, where partially conserved axial current (PCAC) imposes a
relation between the neutrino-production cross section and the one induced by
pions. A dramatic breakdown of the Adler relation (AR) for diffractive
neutrino-production of pions, caused by absorptive corrections, was revealed
recently in arXiv:1105.1711. Indeed, comparing with the cross section predicted
by the dipole phenomenology at $Q^{2}\to0$ on a proton target we confirmed the
sizable deviation from the value given by the AR, as was estimated in
arXiv:1105.1711 within a simplified two-channel model. The dipole approach also
confirms that in the black-disc limit, where the absorptive corrections
maximize, the diffractive cross section ceases, on the contrary to the
expectation based on PCAC.
