  Considering $CuO_{2}$ conducting layers present in high Tc superconductors as
plasma sheets, we proposed a prescription for the $T_{c}$ pressure behavior
taken into account the Casimir effect. The Casimir energy arises from these
parallel plasma sheets (Cu-O planes) when it take placed in the regime of
nanometer scale (small \textit{d} distance). The charge reservoir layer
supplies carries to the conducting $nCuO_{2}$ layers, which are a source of
superconductivity. The pressure induced charge transfer model (PICTM) makes use
of an intrinsic term, which description is still unclear. Considering Casimir
energy describing the $T_{c}$ for the case of hight-$T_{c}$ superconductors, we
propose an explicit expression to the intrinsic term. Realistic parameters used
in the proposed expression have shown an agreement with experimental intrinsic
term data observed in some high-$T_{c}$ compounds.
