title: Pineal N-acetyltransferase activity in hamsters maintained in shortened light cycles.
abstract: Pineal serotonin N-acetyltransferase activity (NAT) was compared among Syrian hamsters maintained in light: dark (LD) cycles of 14:10 or 2:22 or in an interrupted (LD 1/4:53/4 X 4) photoperiodic cycle. In hamsters maintained in a LD 14:10 photoperiod, the zenith of pineal NAT activity occurs at 04:00 h, approximately 8 hours after the onset of the dark phase. When the onset of the dark phase was advanced by 8 hours (in hamsters maintained in LD 2:22 cycles), the pineal NAT activity was advanced by an equivalent length of time. Hamster pineal NAT activity was suppressed throughout a 24-hour period when the animals were maintained in darkness interrupted with brief periods of light at 6 h intervals (LD 1/4:53/4 X 4). The results suggest that melatonin synthesis is determined according to when light occurs during the photoperiodic cycle rather than by the total amount of darkness or the dark: light ratio to which animals are exposed in a 24-hour period.
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism*; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism*; D002940:Circadian Rhythm; D006224:Cricetinae; D003624:Darkness; D008027:Light; D008297:Male; D008647:Mesocricetus; D010870:Pineal Gland / Q000201:enzymology*
chemical_list: D000123:Acetyltransferases; D001191:Arylamine N-Acetyltransferase