Author/Editor		Inoue, Shojiro
Title		Vitamin B12 amplifies circadian phase-shifting effects of light pulse and melantionin in rats
Type		članek
Source		In: Hočevar A, Črepinšek Z, Kajfež-Bogataj L, editors. Biometeorology 14. Proceedings of the 14th international congress of biometeorology. Part 2. (Vol 2); 1996 Sep 1-8; Ljubljana. Ljubljana: Slovenian meteorological society,
Publication year		1996
Volume		str. 303-10
Language		eng
Abstract		Vitamin VB12 (VB12), a circadian clock modulator, was investigates as to its effects on light pulse (LP)- and melatonin-induced phase shifts of drinking activity rhythm in male rats freerunning under constant dim illumination (0.5-1.0 lux). A single LP 50-1000 lux for 20 min given at circadian time (CT) 20 induced a 0.28 to 1.08-h phase advance and at CT 14 induced a 0.54 to 2.10-h phase delay. A 3-h intracerebroventricular infusion of 30 nmol VB12 starting 2 h prior to a 200-lux LP significantly amplified phase shifts in comparison with saline-treated or untreated controls. The mean phase advance (1.13 h) was 1.8-fold greater than that of saline-infused controls, whereas the mean phase delay (2.28 h) was 2.9-fold greater. These values were comparable to the maximal phase shift caused by 100-lux LPs in untreated rats. Thus VB12 enhanced LP-induced phase shifts and augmented the entrainability of the circadian clock to light. A single intraperitoneal (ip_ injection of melationin (1 micro g/kg) at CT 10 induced a 0.25-h phase advance. A single ip injection of VB12 (500 micro g/kg) 30 min prior to the melatonin treatment significantly amplified the effect of melatonin, inducing a 0.65-h phase advance. This value was comparable to the phase shift caused by higher doses (10-100 micro g/kg) of mealatonin ip given at CT 10. Since the same administration of VB12 alone exerted no effect on phase shift, it is likely that VB12 enhanced melatonin-induced phase shifts and augmented the entrainability of the circadian clock to melatonin. In conclusion, VB12 amplified circadian phase-shifting effects of both LPs and melatonin in freerunning rats.
Descriptors		CIRCADIAN RHYTHM DRINKING MELATONIN VITAMIN B 12 RATS, SPRAGUE-DAWLEY