EN
In this work we investigate the conductivity in the basis plane of YBa_2Cu_3O_{7-x} and Y_{1-z}Pr_zBa_2Cu_3O_{7-x} single crystals with a system of one-direction twin boundaries. The Pr dopants behave as efficient scattering centers of normal and fluctuating carriers. For this a slight doping with praseodymium (till z≈0.05) results in a significant narrowing of the temperature interval in which the pseudo-gap regime is realized in the ab-plane of YBaCuO single crystals.