Red light suppresses N-acetylserotonin but does not elevate 5-HT and 5-HIAA of the rat pineal glands at night.

HPLC with EC detector was used to study the red light effect on the rhythmicity of catecholamines (NE, DOPAC and dopamine) and indoleamines (NAS, 5-HT, 5-HIAA) in the pineal glands and retinas of the Sprague-Dawley rat. We found the prominent nocturnal elevations of NAS in rat pineal glands and the suppression of the NAS but not the elevation of 5-HT and 5-HIAA after red light exposure at night. Our data show two findings: metabolic pathway of the indoleamines (5-HT, 5-HIAA and NAS) after red light exposure at night may be different from those by white light. Second, the increased HIOMT activity that effects on 5-HT and 5-HIAA may also be involved in the indoleamine formation after red light exposure at night.