Jb. Zawilska et al., EFFECTS OF NEAR-ULTRAVIOLET LIGHT ON THE NOCTURNAL SEROTONIN N-ACETYLTRANSFERASE ACTIVITY OF RAT PINEAL-GLAND, Neuroscience letters, 243(1-3), 1998, pp. 49-52
Effects of near-ultraviolet (UV-A; 325-390 nm, peak at 365 nm) light o
n the activity of the pineal serotonin N-acetyltransferase (NAT; a pen
ultimate and key regulatory enzyme in melatonin biosynthesis) were exa
mined in rats. Acute exposure of dark-adapted animals to UV-A radiatio
n produced a marked suppression of NAT activity of the pineal gland, t
he effect being dependent on exposure time. The decrease in the night-
time NAT activity evoked by a 1-min pulse of UV-A light (as well as by
a 15-s pulse of broad-band visible light) gradually deepened during t
he first 40 min of treatment of animals with constant darkness, then t
he enzyme activity began to rise reaching control values by 3 h. Treat
ment of rats with a protein synthesis inhibitor, cycloheximide, attenu
ated this night-driven reactivation of the pineal NAT activity. The pr
esented results provide evidence that UV-A light is a powerful signal
capable of controlling melatonin biosynthesis in rat pineal gland. (C)
1998 Elsevier Science Ireland Ltd.