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Phase Response Curves to Neuropeptide Y in Wildtype and Tau Mutant HamstersDepartments of Zoology and Physiology, University of Toronto, Toronto, Ontario M5S 1A1, Canada
Departments of Zoology and Physiology, University of Toronto, Toronto, Ontario M5S 1A1, Canada Neuropeptide Y (NPY)-containing fibers project from the intergeniculate leaflet to the suprachiasmatic nucleus. NPY has been shown to phase shift the circadian locomotor activity rhythm of wildtype hamsters, producing large phase advances in the subjective day and small delays in the subjective night. Previous studies have implicated this pathway in the mediation of activity-induced resetting of the circadian clock. Homozygous tau mutant and wildtype hamsters respond very differently to pulses of activity Not only is the amplitude of the phase response curve exaggerated in the mutants with shifts of up to 7 h, but the stimuli are effective at different times during the cycle. Homozygous tau mutant hamsters and wildtype controls were implanted with guide cannulas aimed at the suprachiasmatic nucleus and injected with NPY at various times during the circadian cycle. The responses of homozygous tau mutant hamsters to NPY resembled their responses to nonphotic stimuli in both timing and direction of phase shift. This finding provides correlational evidence that NPY is involved in the effects of nonphotic behavioral events on the circadian system.
Key Words: NPY • circadian • wheel running • hamster • suprachiasmatic nucleus • activity
Journal of Biological Rhythms, Vol. 11, No. 1,
27-34 (1996) This article has been cited by other articles:
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