  We investigate electric field effects in thin film microbridges of
La$_{0.7}$Ca$_{0.3}$MnO$_3$ with the focus on the regime of metal-insulator
transition. A mechanically milled SrTiO$_3$ substrate is used as a backgate
dielectric. Inside the metal-insulator transition we find a strong unipolar
field-induced reduction in resistance, as well as a suppression of the
nonlinear features in the I-V curves we observed earlier. We associate the
observed effects with a phase separated state in which metallic regions coexist
with short range correlated polaron regions. When the glassy polaron phase has
fully developed, and closes off the microbridge, the field effects disappear
leaving the strongly nonlinear behavior of the transport current unaltered.
