Diurnal rhythms in pineal N-acetyltransferase and hippocampal norepinephrine: effects of water deprivation, blinding and hypothalamic lesions.
The pineal gland in the rat exhibits a diurnal rhythm in activity of the enzyme serotonin N-acetyltransferase (N-AT) with peak values during the dark period of a diurnal lighting schedule approximately 100-fold those during the light period. After blinding the rhythm becomes free-running. It is abolished by partial hypothalamic deafferentation with a knife cut made caudal to the optic chiasm. Water deprivation for 23 h daily has no effect on the pineal rhythm in either intact, blinded or deafferented animals. In contrast to this, there is a diurnal rhythm in hippocampal formation in norepinephrine content which can be entrained by a water deprivation schedule in both intact and blinded animals. These observations indicate that in the same animals 1 diurnal rhythm may remain entrained to the light-dark cycle while another rhythm is entrained to a secondary synchronizer, the water deprivation schedule.
D000123:Acetyltransferases / Q000378:metabolism*; D000818:Animals; D001766:Blindness / Q000378:metabolism; D002940:Circadian Rhythm; D003624:Darkness; D005260:Female; D006624:Hippocampus / Q000378:metabolism*; D007031:Hypothalamus / Q000502:physiology; D008027:Light; D009475:Neurons, Afferent / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism; D010870:Pineal Gland / Q000201:enzymology*; D051381:Rats; D012701:Serotonin / Q000378:metabolism; D014795:Visual Pathways / Q000502:physiology; D014868:Water Deprivation
D012701:Serotonin; D000123:Acetyltransferases; D009638:Norepinephrine