Ramelteon (TAK-375) is a Melatonin Receptor Agonist. The mechanism of action of ramelteon is as a Melatonin Receptor Agonist.

MT receptor (chicken):23.1 pM(Ki), MT2 receptor:112 pM(Ki), MT1 receptor:14 pM(Ki)

cDNA encoding the human MT1 gene is introduced into CHO cells. Cells are harvested at confluence in Ca2+ and Mg2+ free Hanks' balanced salt solution containing 5 mM EDTA and collected by centrifugation. Cells are homogenized in ice-cold 50 mM Tris–HCl buffer, washed twice, pelleted, and stored at -30°C until the binding assays are conducted. Test compound and 40 pM 2-[ 125I]melatonin are mixed with the thawed homogenate in a total volume of 1 mL and incubated at 25°C for 150 min. The reaction is terminated by addition of 3 mL of icecold buffer followed by vacuum filtration on a Whatman GF/B. The filter is washed twice and radioactivity is counted by a g-counter[1].