Carrier doping effects on electronic correlations in La_1-xSr_xTiO₃ have been investigated by ^47/49Ti and ¹³⁹La NMR. The increases of nuclear spin-lattice relaxation rates, (T1T)^-1, of both La and Ti provide the critical enhancements of effective carrier mass on approaching the Mott transition phase boundary from the metallic side. We have no evidences for a prominent increase of antiferromagnetic spin fluctuations at q〜Q near the Mott-transition boundary, which is sharply contrast to the case of high-TC cuprates.