27881
In the ovine PT , melatonin is known to influence acute changes in transcriptional dynamics coupled to the onset ( dusk ) and offset ( dawn ) of melatonin secretion , leading to a potential interval - timing mechanism capable of decoding changes in day - length ( photoperiod ) .
 Chemical: melatonin; Chemical: melatonin
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: melatonin; Chemical: melatonin