  We develop a general technique to calculate the probability of transitions
over the barriers in spin-glasses in the framework of the dynamical theory. We
use Lagrangian formulation of the instanton dynamics in which the transitions
are represented by instantons. We derive the full set of the equations that
determine the instantons but instead of solving them directly we prove that an
instanton process can be mapped into a usual process going back in time which
simplifies the problem significantly. We apply this general considerations to a
simple example of the spherical Sherrington-Kirkpatrick model and we find the
probability of the transition between the metastable states which is in
agreement with physical expectations.
