  We studied the evolution of the gas kinematics of galaxies by performing
hydrodynamical simulations in a cosmological scenario. We paid special
attention to the origin of the scatter of the Tully-Fisher relation and the
features which could be associated with mergers and interactions. We extended
the study by De Rossi et al. (2010) and analysed their whole simulated sample
which includes both, gas disc-dominated and spheroid-dominated systems. We
found that mergers and interactions can affect the rotation curves directly or
indirectly inducing a scatter in the Tully-Fisher Relation larger than the
simulated evolution since z=3. In agreement with previous works, kinematical
indicators which combine the rotation velocity and dispersion velocity in their
definitions lead to a tighter relation. In addition, when we estimated the
rotation velocity at the maximum of the rotation curve, we obtained the best
proxy for the potential well regardless of morphology.
