Noradrenaline (NAd, norepinephrine) is a neurotransmitter whose action is mediated by the noradrenaline transporter NAT1. NAT1 is a monoamine transporter that transports noradrenaline from the synapse back to its vesicles for storage until later use. NAT1 is encoded by the human gene SLC6A2 and is expressed in the CNS and adrenal gland (Pacholczyk et al. 1991). Defects in SLC6A2 results in orthostatic intolerance (OI), which is a syndrome characterized by lightheadedness, fatigue and development of symptoms during upright standing, relieved by sitting back down again (Shannon et al. 2000).