Circadian rhythms in serotonin, norepinephrine, and epinephrine contents of the pineal-paraphyseal complex of the soft-shelled turtle (Lissemys punctata punctata).

Diurnal variations in pineal serotonin, norepinephrine, and epinephrine levels were measured at four different time intervals (06:00, 12:00, 18:00, and 24:00 hr) in adult male soft-shelled turtles. The serotonin level increased during day and decreased during night. But the norepinephrine and epinephrine levels showed reverse changes. The findings reveal that there is a distinct circadian rhythm in serotonin, norepinephrine, and epinephrine contents of the pineal-paraphyseal complex in adult male soft-shelled turtles.