  We have reported the effect of pressure on the magnetization, and transport
properties in the nominal composition Pr$_{2}$Ba$_{4}$Cu$_{7}$O$_{15-\delta}$
synthesized by a sol-gel technique. A reduction treatment of the as-sintered
sample in vacuum causes higher superconductivity achieving $T_{c,on}=\sim 30$ K
for $\delta =0.94$. Application of hydrostatic pressure on the oxygen depleted
sample enhances its onset temperature up to 36 K at 1.2 GPa, indicating the
nearly optimum doping level of the charge carrier in comparison to the pressure
dependence of lower $T_{c}$ samples with $\delta =0.45$. Seebeck coefficient of
the superconducting sample shows a metallic conduction, followed by a clear
drop below $T_{c,on}$ and is in its temperature dependence below 100 K quite
different from that of the non-superconducting one. This finding strongly
suggests a dramatic change of the electronic state along the CuO double chain
due to the reduction treatment for the appearance of superconductivity .
