  We study the dynamics of a charged spin-1/2 particle in an external
5-dimensional electromagnetic field. We then consider that we are at the $TeV$\
scale, so that we can access the fifth dimension and carry out our physical
considerations in a 5-dimensional brane. In this brane, we focus our attention
to the quantum-mechanical dynamics of a charged particle minimally coupled to
the 5-dimensional electromagnetic field. We propose a way to identify the
Abraham-Lorentz back reaction force as an effect of the extra (fifth)
dimension. Also, a sort of dark matter behavior can be identified in a
particular regime of the dynamics of the particle interacting with the bulk
electric field.
