5-Methoxytryptophol rhythms in the chick pineal gland: effect of environmental lighting conditions

• Published in: Neuroscience letters 1998-07, Vol.251 (1), p.33-36
• Main Authors: Zawilska, Jolanta B, Skene, Debra J, Nowak, Jerzy Z
• Format: Article
• Language: English
• Subjects: 5-Methoxytryptophol; Animals; Biological and medical sciences; Chick; Chickens; Chronobiology; Circadian rhythm; Circadian Rhythm - physiology; Circadian Rhythm - radiation effects; Darkness; Fundamental and applied biological sciences. Psychology; Indoles - metabolism; Light; Lighting; Male; Melatonin; Melatonin - metabolism; Pineal gland; Pineal Gland - metabolism; Pineal Gland - radiation effects; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0304-3940; 1872-7972
• DOI: 10.1016/S0304-3940(98)00481-9

5-Methoxytryptophol (5-ML) rhythms were studied in the pineal glands of chicks which were adapted to three different lighting conditions: 12 h light: 12 h dark (LD), constant darkness (DD) and continuous light (LL). Pineal glands of chicks kept under LD conditions exhibited rhythmic fluctuations in 5-ML content. 5-ML levels were low (18±2 pg/pineal) during the dark phase of the cycle, they increased approximately 9-fold at the end of the dark phase, and remained high (176±6 pg/pineal) throughout the light period. This pattern of 5-ML content also persisted under conditions of DD, indicating that the 5-ML rhythm is circadian in nature. This is the first evidence of circadian rhythmicity of 5-ML. Pineal 5-ML levels in chicks kept under LL were high (168±8 pg/pineal), but did not fluctuate in a rhythmic fashion. Under LD and DD, but not LL, the rhythm of 5-ML in the chick pineal is 180° out of phase with the rhythm of melatonin biosynthesis, an observation suggesting that, at least in this species, the pineal production of these two hormones may be inversely correlated.