Light-Induced Phase Shifts in tau Mutant Hamsters

Kazuhiro Shimomura, Michael Menaker

Research output: Contribution to journalArticlepeer-review

68 Scopus citations

Abstract

Phase shifts produced by single 1-hr light pulses were compared in homozygous tau mutant and wild-type hamsters after several different kinds of pretreatment regimens. There was a dramatic increase in the magnitude of phase delays in the mutant hamsters as they were kept for progressively longer times in constant darkness (DD), and a smaller increase in the magnitude of phase advances. Under the same conditions a small increase in the magnitude of phase delays and no significant increase in phase advances occurred in the wild-type hamsters. After only 7 days in DD the phase response curves (PRCs) of mutant and wild-type hamsters were both type 1 and were indistinguishable from each other, whereas after 49 days in DD the PRCs of mutant hamsters had become type 0. Mutant hamsters were entrained to eight different T-cycles (1 hr of light per cycle), released into DD, and given a phase delaying light pulse 7 days later. T-cycles which entrained the animals so that the 1 hr of light fell between 6 and 9 hours after the onset of activity suppressed the amplitude of phase delays, whereas T-cycles which entrained the animals so that the 1 hr of light fell at other times did not suppress phase delays. The implications of the data for entrainment theory and the mechanism of action of the tau gene are discussed.

Original languageEnglish (US)
Pages (from-to)97-110
Number of pages14
JournalJournal of biological rhythms
Volume9
Issue number2
DOIs
StatePublished - Jul 1994

Keywords

  • T-cycles
  • circadian aftereffects
  • circadian mutation
  • circadian rhythms
  • hamster
  • locomotor activity
  • phase response curve
  • phase shifts

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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