. 2010 Sep;62(3):343–380. doi: 10.1124/pr.110.002832

TABLE 1.

IUPHAR melatonin receptor nomenclature and classification

Nomenclature	MT₁	MT₂	MT₃
Previous names	MEL_1A, ML_1A, Mel_1a	MEL_1B, ML_1B, Mel_1b	ML₂
Structural information	7TM	7TM
Gene/chromosome
Human	350 aa,^a P48039; chr 4q 35.1	362 aa,^b P49286; chr 11q21–22
Mouse	353 aa,^c Q61184; chr 8	365 aa,^d U57554; chr 9
Selective agonists	S 26284^e	IIK7 (10.3)^f	N-Acetylserotonin,^g–k 5MCA-NAT^k
Selective antagonists	S 26131^e	4P-ADOT,^l,m 4P-PDOT (8.8),^l,m GR 128107^l, K185 (9.3)^f	Prazosin^h
Radioligands	[³H]MLT,ⁿ 2- [¹²⁵I]IMLT^o	[³H]MLT,ⁿ 2-[¹²⁵I]IMLT,^o [³H]4P-PDOT^p	2-[¹²⁵I]5MCA-NAT,^k 2-[¹²⁵I]IMLTⁿ
Tissue Functions	Vascular vasoconstriction,^q–u inhibition neuronal firing,^v phase-shift circadian activity rhythms^u	Vascular vasodilation,^t inhibition retinal dopamine release,^l phase-shift circadian rhythms of neuronal firing^m,w,v,x	Leukocyte adhesion^u
Comments	MT₁ full-length cDNAs were cloned from human (350 aa),^a mouse (353 aa),^c sheep (366 aa),^a rat (353 aa),^y hamster (353 aa),^z monkey (352),^aa and partial cDNAs from cattle (257 aa) and pig (154 aa).^bb	MT₂ cDNA was cloned from human (362 aa),^z rat (364 aa),^y mouse (365 aa),^d sheep (376 aa),^cc monkey (362 aa),^aa and partial cDNA from hamster.^z	Endogenous ligands are MLT and N-acetylserotonin. A recent report identifies an MT₃ binding site in hamster kidney as the enzyme quinone reductase-2.^dd Antagonist potencies have not yet been established.