We discuss the effect of the spin-orbit interaction on the band structure, wave functions and low temperature conductance of long quasi-one-dimensional electron systems patterned in two-dimensional electron gases (2DEG). Our model for these systems consists of a linear (Rashba) potential confinement in the direction perpendicular to the 2DEG and a parabolic confinement transverse to the 2DEG. We find that these two terms can significantly affect the band structure introducing a wave vector dependence to subband energies, producing additional subband minima and inducing anticrossings between subbands. We discuss the origin of these effects in the symmetries of the subband wave functions.