"" class="an ">&ensp;</span>results <span  title="" class="an ">&ensp;</span>are <span  title="" class="an ">&ensp;</span>most <span  title="" class="an ">&ensp;</span>simply <span  title="" class="an ">&ensp;</span>explained <span  title="" class="an ">&ensp;</span>by <span  title="" class="an ">&ensp;</span>the <span  title="" class="an ">&ensp;</span>formation <span  title="" class="an ">&ensp;</span>of <span  title="" class="an ">&ensp;</span>heteromeric <span  title="" class="an ">&ensp;</span>channels