  We investigate a general parabolic initial-boundary value problem with zero
Cauchy data in some anisotropic H\"ormander inner product spaces. We prove that
the operators corresponding to this problem are isomorphisms between
appropriate H\"ormander spaces. As an application of this result, we establish
a theorem on the local increase in regularity of solutions to the problem. We
also obtain new sufficient conditions under which the generalized derivatives,
of a given order, of the solutions should be continuous.
