Table 1. Daytime levels of N-acetyltryptamine and melatonin in rat, human and rhesus macaque plasma.

Data represent the mean ± SEM for plasma N-acetyltryptamine and melatonin from the indicated number of individuals; individual values were calculated from the mean of three or more determinations of the sample. Rat plasma samples were drawn between 13:00 and 14:00 h; human plasma samples between 07:00 h and 14:00 h and the rhesus samples between 09:00 and 15:00 h. Additional experimental details appear in the Materials and Methods section.

	Plasma Concentration
Source	N-Acetyltryptamine [nM]	Melatonin [nM]	N-Acetyltryptamine/ Melatonin
Rat (N=5)	0.29 ± 0.05	0.17 ± 0.01	1.7
Human (N=32)	0.03 ± 0.01	0.06 ± 0.01	0.5
Rhesus (N=4)	0.5 ± 0.2	0.17 ± 0.06	2.9