  The doped cuprates are considered to be a system of local spinless bosons
moving in a lattice of the hole pseudo-Jahn-Teller centers CuO_{4}^{5-}. A
detailed qualitative and quantitative description of the vibronic mechanism
determining both the isotope substitution and the external pressure effect on
T_c is given. This mechanism can properly interpret the principal peculiarities
of isotopic and baric effects in cuprates except the region of the well
developed percolation phenomena
