title: Circadian rhythms in firing rate of individual suprachiasmatic nucleus neurons from adult and middle-aged mice.
abstract: The suprachiasmatic nucleus contains a biological clock that drives circadian rhythms in vivo and in vitro. It has been suggested that the suprachiasmatic nucleus is a primary target of the aging process, because age-related changes in behavioral rhythms are mirrored in alterations in circadian pacemaker function. Using long-term, single-cell recording, we assessed the effect of age on firing-rate patterns of individual suprachiasmatic nucleus neurons of young adult (2-4 months) and middle-aged (9-11 months) C3H mice. Individual suprachiasmatic nucleus neurons from adult mice maintained in culture for at least one week exhibited robust circadian rhythms in spontaneous activity that were similar in the free-running period (23.7+/-0.3 h mean+/-S.E.M.) to recordings from neurons dispersed from neonatal tissue, and showed evidence of entrainment to prior light cycles by exhibiting peak activity, in vitro, approximately 4.0+/-0.3 h (mean+/-S.E.M.) after the time of expected light onset. Aging led to a decreased amplitude of impulse activity in dispersed suprachiasmatic nucleus neurons and increased variability in the circadian waveform. From these results we suggest that age-related deterioration in circadian clock function occurs at the level of individual cells, which may account for some of the age-related deficits observed in the expression of behavioral rhythmicity.
authors.affiliation: Laboratoire d'Ecologie Générale, UMR CNRS 8571, 4 avenue du Petit Château, 91800 Brunoy, France. fabienne.aujard@wanadoo.fr
authors.forename: F
authors.initials: F
authors.lastname: Aujard
authors.forename: E D
authors.initials: ED
authors.lastname: Herzog
authors.forename: G D
authors.initials: GD
authors.lastname: Block
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000375:Aging / Q000502:physiology*; D000818:Animals; D018929:Cell Culture Techniques / Q000379:methods; D002478:Cells, Cultured / Q000166:cytology / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology*; D004594:Electrophysiology / Q000379:methods; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D009043:Motor Activity / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000502:physiology*