title: Circadian rhythm in pineal N-acetyltransferase activity: phase shifting by dark pulses (III).
abstract: N-Acetyltransferase (NAT) is an enzyme whose rhythmic activity in the pineal gland and retina is thought to be responsible for melatonin circadian rhythms. The enzyme has circadian properties--its rhythm persists in constant conditions, and it is precisely controlled by light and dark. Experiments are reported in which 4-h light or dark pulses were imposed on chicks (Gallus domesticus) over a 24-h period. Pineal NAT profiles were measured during and subsequent to the pulses. The phase of the NAT cycle following pulses was plotted to obtain phase-response curves. Light pulses produced a maximum phase shift (advance of 5 h) 8 h after the expected time of lights-out; dark pulses produced a maximum phase shift (advance of 4 h) 3 h after the expected time of lights-out. Maximum phase delays (-2 h) occurred 1-2 h after the expected lights-out for light pulses and 8 h after expected lights-on for dark pulses.
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism*; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism* / Q000502:physiology; D002645:Chickens; D002940:Circadian Rhythm; D003624:Darkness; D010870:Pineal Gland / Q000201:enzymology* / Q000502:physiology; D013997:Time Factors
chemical_list: D000123:Acetyltransferases; D001191:Arylamine N-Acetyltransferase