  Light-sheet fluorescence microscopy (LSFM) makes use of a thin plane of light
to optically section and image transparent tissues or organisms {\it{in vivo}},
which has the advantages of fast imaging speed and low phototoxicity. In this
paper, we have employed light-sheet microscopy to investigate the polarization
effects on fluorescence emission of zebrafish neurons via modifying the
electric oscillation orientation of the excitation light. The intensity of the
fluorescence emission from the excited zebrafish larvae follows a cosine square
function with respect to the polarization state of the excitation light and
reveals a 40$\%$ higher fluorescence emission when the polarization orientation
is orthogonal to the illumination and detection axes. Through registration and
subtraction of fluorescence images under different polarization states, we have
demonstrated that most of the enhanced fluorescence signals are from the nerve
cells rather than the extracellular substance. This provides us a way to
distinguish the cell boundaries and observe the organism structures with
improved contrast and resolution.
