PubMed · 7205514
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C N Jacklin, M E Snow, M Gahart, E E Maccoby. 1980. Sleep pattern development from 6 through 33 months.. https://doi.org/10.1093/jpepsy%2F5.3.295
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Substantial progress has been made in understanding the genetic basis of temperature-compensated circadian clocks. Ultradian rhythms, with a period shorter than 24 h, are at least as widespread as circadian rhythms. We have initiated genetic analysis of defecation behavior, which is controlled by an ultradian clock in Caenorhabditis elegans. The defecation motor program is activated every 45 sec, and this rhythm is temperature compensated. We describe mutations in 12 genes that either shorten or lengthen the cycle period. We find that most of these mutations also disrupt temperature compensation, suggesting that this process is an integral part of the clock. These genes open the way for molecular genetic dissection of this ultradian clock.
Seasonal changes of daylength (photoperiod) affect the expression of hormonal and behavioral circadian rhythms in a variety of organisms. In mammals, such effects might reflect photoperiodic changes in the circadian pace-making system [located in the suprachiasmatic nucleus (SCN) of the hypothalamus] that governs these rhythms, but to date no functionally relevant, intrinsic property of the SCN has been shown to be photoperiod dependent. We have analyzed the temporal regulation of light-induced c-fos gene expression in the SCN of rats maintained in long or short photoperiods. Both in situ hybridization and immunohistochemical assays show that the endogenous circadian rhythm of light responsiveness in the SCN is altered by photoperiod, with the duration of the photosensitive subjective night under the short photoperiod 5-6 h longer than under the long photoperiod. Our results provide evidence that a functional property of the SCN is altered by photoperiod and suggest that the nucleus is involved in photoperiodic time measurement.
The EEG signal of the area hypothalami posterior (PH) was recorded in the urethane anaesthetized rat. The main characteristic of the EEG in this brain region was intermittent oscillations of high amplitude in the delta and theta frequency bands. Oscillations of the alpha and beta frequency bands showed comparatively lower variations. Time distribution analysis of the EEG spectral power revealed that the delta and theta rhythms appeared and disappeared according to an ultradian rhythm with a frequency of approximately 1 cycle per 100 min. No significant rhythm was found in the alpha and beta band. The rhythm frequency of neuronal activity in the PH is very similar to the ultradian frequency of pulsatile neurotransmitter release in the PH demonstrated previously.