Plasma membrane monoamine transporters (PMAT) is a monoamine transporter which has functional and structural similarities to the organic cation transporters (OCT) family^1,2. PMAT first cloned in 2004 from the human brain. PMAT transporter belongs to the equilibrative nucleoside transporter (ENT) family but it functions as a polyspecific organic cation transporter³. PMAT (ENT4) has a low-affinity and high-capacity for monoamines ^3,4. It was identified as a sodium-independent, electrogenic cation transporter with a wide range of substrates. The protein contains 530 amino acids with 11 transmembrane domains, very similar to the organic cation transporters (OCT) family. A peculiarity of this transporter is its ability to function bidirectionally ^1,2,4. PMAT is highly expressed in the brain and skeletal muscle and also found in the liver, kidney, intestine and heart. It efficiently transports many organic cations such as 1-methyl-4-phenylpyridinium (MPP+), which is also the case for OCTs. In particular, PMAT transports histamine with a low affinity but efficiently (high Vmax) ^4,5. Similarly, both PMAT and OCTs are sensitive to decynium-22 blockade ^4,6. However, PMAT was insensitive to the steroid corticosterone, unlike OCTs 3. Direct comparison of transport efficiency (Vmax/Km) between human OCT3 and PMAT expressed in HEK cells found that 5-HT and dopamine were preferentially taken up by PMAT. Alternatively, OCT3 has a higher preference for histamine, noradrenaline and adrenaline over other biogenic amines ⁷. The same study found that PMAT was insensitive to inhibitors of high-affinity monoamine transporters such as citalopram, GBR-12909 and desipramine. An earlier study substantiated this by showing a range of antidepressant and antipsychotic drugs had IC50’s of 10-20µM at the human PMAT⁸. PMAT distribution has been investigated in mouse and rat brain^9,10. PMAT reported to be widely distributed throughout the brain and not necessarily associated with monoamine pathways. Indeed, it was completely absent from the rat substantia nigra. Expression of PMAT has been reported to be primarily neuronal. Cells double labeled with glial fibrillary acidic protein and PMAT were not observed in any great number in the mouse brain⁹. However, there is evidence PMAT expression in cultured human astrocytes where they mediate histamine transport¹¹.