="an ">&ensp;</span>activity <span  title="" class="an ">&ensp;</span>in <span  title="" class="an ">&ensp;</span>heart <span  title="" class="an ">&ensp;</span>and <span  title="" class="an ">&ensp;</span><span  title="BrainRegionP" class="an BrainRegionP">brain</span><span  title="" class="an ">&ensp;</span>The <span  title="" class="an ">&ensp;</span>four <span  title="" class="an ">&ensp;</span><span  title="CAP" class="an CAP">HCN</span><span  title="" class="an ">&ensp;</span>isoforms <span  title="" 