 class="an ">&ensp;</span>monoaminergic <span  title="" class="an ">&ensp;</span>neurotransmitter <span  title="" class="an ">&ensp;</span>systems <span  title="" class="an ">&ensp;</span>play <span  title="" class="an ">&ensp;</span>a <span  title="" class="an ">&ensp;</span>central <span  title="" class="an ">&ensp;</span>role <span  title="" class="an ">&ensp;</span>in <span  title="" class="an ">&ensp;</span>reward <span  title="" class="an ">&ensp;</span>processing <span  title="" class="an ">&ensp;</s