The level of N-acetylserotonin and melatonin in the brain of male rats: Diurnal variations and effects of pinealectomy

✍ Scribed by Pang, S. F. ;Tang, P. L. ;Yu, H. S. ;Yip, M. K.

• Publisher: John Wiley and Sons
• Year: 1982
• Tongue: English
• Weight: 485 KB
• Volume: 219
• Category: Article
• ISSN: 0022-104X
• DOI: 10.1002/jez.1402190302

✦ Synopsis

Abstract

The levels of N‐acetylserotonin and melatonin (n‐acetyl‐5‐methoxytryptamine) in the rat brain were studied. Male rats were housed under a photoperiod of 12L:12D. After 2 weeks, the rats were sacrificed in light or in dark at 4‐hour intervals round the clock. Brain melatonin and N‐acetylserotonin were extracted by chloroform at ⩾ pH 10 and ethyl acetate at ⩽ pH 3 respectively and quantified by radioimmunoassay. There was a circadian rhythm of brain melatonin (F < 0.05) with a nadir at 1600 h and a zenith at 0400 h. Brain N‐acetyl‐serotonin, unlike brain melatonin, demonstrated no diurnal variation. Effects of pinealectomy on brain N‐acetylserotonin and melatonin were also studied. Male rats were housed as noted. After 2 weeks, they were pinealectomized or shamoperated. The animals were killed in light or in dark 1 week after operation. The levels of brain melatonin at 2400 h and 0400 h were significantly lowered (P < 0.5) following pineal removal. Pinealectomy, however, has no observable effect on the level of brain N‐acetylserotonin. Our findings suggest that (1) there is a diurnal rhythm of brain melatonin, (2) the elevation of brain melatonin in the dark period is dependent on the pineal, (3) brain N‐acetylserotonin has no diurnal variation, and (4) brain N‐acetylserotonin is not affected by pinealectomy.