In a previous study, the decreased expression of SLC6A2 in humans was reported to elevate norepinephrine levels and lead to a high heart rate in postural tachycardia syndrome (POTS)31, which might be associated with the high resting heart rate (600–700 bpm) of the zebra finch32. The gene discussed is SLC6A2; the disease is postural orthostatic tachycardia syndrome.