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]IMLT^ⁿ
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.

aa, amino acid(s); chr, chromosome; 5MCA-NAT, 5-methoxycarbonylamino-N-acetyltryptamine.
↵a Reppert et al., 1994.
↵b Reppert et al., 1995a.
↵c Roca et al., 1996.
↵d Jin et al., 2003.
↵e Audinot et al., 2003.
↵f Faust et al., 2000.
↵g Dubocovich, 1988b.
↵h Lucchelli et al., 1997.
↵i Eison and Mullins, 1993.
↵j Popova and Dubocovich, 1995.
↵k Molinari et al., 1996.
↵l Dubocovich et al., 1997.
↵m Dubocovich et al., 1998b.
↵n Browning et al., 2000.
↵o Dubocovich and Takahashi, 1987.
↵p Dubocovich and Masana, 1999.
↵q Ting et al., 1999.
↵r Ting et al., 1997.
↵s Masana et al., 2002.
↵t Doolen et al., 1998.
↵u Lotufo et al., 2001.
↵v Liu et al., 1997.
↵w Dubocovich et al., 2005.
↵x Hunt et al., 2001.
↵y Audinot et al., 2008.
↵z Weaver et al., 1996.
↵aa Nishiyama et al., 2009.
↵bb Messer et al., 1997.
↵cc Cogé et al, 2009.
↵dd Nosjean et al., 2000.