4760
The most potent subtype - selective ligand , 2q had a substantially higher potency for MT ( 2 ) receptor than melatonin for elevation of [ Ca ( 2 + ) ] i and inhibition of forskolin - elevated cAMP .
 melatonin, Ca ( 2 + )
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 melatonin, Ca ( 2 + )