title: Circadian oscillation of the multiple unit activity in the guinea pig suprachiasmatic nucleus.
abstract: In the guinea pig with chronically implanted electrodes, neuronal multiple unit activity (MUA) was recorded inside and outside the suprachiasmatic nucleus (SCN). Long-term recording of the SCN indicated distinct daily rhythms with a daytime peak in MUA during a 24-h light-dark (LD 12:12) cycle. On the other hand, MUA recorded from adjacent hypothalamic regions outside the SCN showed a phase reversal with a nighttime peak, similarly to the rat. The amplitude of the rhythms recorded outside the SCN was much smaller (one-half to one-quarter) than that inside the SCN. These rhythms persisted during constant darkness indicating characteristics of endogenous circadian rhythmicity. When the external light-dark cycle was delayed abruptly for 12 h, MUA rhythms showed a gradual phase shift taking 7-10 days for complete reentrainment. Overt behavior including sleep-wakefulness did not show significant and consistent daily or circadian rhythms in spite of the distinct oscillation in neuronal activity inside the SCN.
authors.affiliation: Department of Neuroscience, Mitsubishi-Kasei Institute of Life Sciences, Tokyo, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Kurumiya
authors.forename: H
authors.initials: H
authors.lastname: Kawamura
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002940:Circadian Rhythm; D004567:Electrodes, Implanted; D004594:Electrophysiology; D006168:Guinea Pigs / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000502:physiology; D012890:Sleep / Q000502:physiology; D013493:Suprachiasmatic Nucleus / Q000502:physiology*