15 Fakultätsübergreifend / Sonstige Einrichtung
Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16
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Item Open Access Phase shifting the circadian clock with cycloheximide : response of hamsters with an intact or a split rhythm of locomotor activity(1989) Wollnik, Franziska; Turek, Fred W.; Majewski, Philip; Takahashi, Joseph S.Systematic administration of the protein synthesis inhibitor, cycloheximide, induced both phase advances and phase delays in the circadian rhythm of wheel-running activity in hamsters (Mesocricetus auratus) maintained in constant darkness or constant light. The magnitude and direction of the phase shifts were dependent on the circadian time (CT) of drug treatment. The phase response curves in constant darkness and constant light were of similar general shape, but they differed in the overall mean amplitude of the phase shifts. Maximal phase advances were observed after injections around CT 6-8, maximal delays at CT 0-2. Injections of various doses of cycloheximide at CT 0 induced a dose-dependent phase delay in the rhythm with a maximum delay induced by 10 mg cycloheximide. Injections of cycloheximide in animals with a split activity rhythm caused phase shifts of both components in the same direction (20/39) and in different directions (10/39). The results support the hypothesis that 80S ribosomal protein synthesis plays an important role in the biochemical mechanisms of circadian systems.Item Open Access SCN lesions abolish ultradian and circadian components of activity rhythms in LEW/Ztm rats(1989) Wollnik, Franziska; Turek, Fred W.A trimodal locomotor activity pattern has been observed in LEW/Ztm rats. Complete and partial lesions of the suprachiasmatic nucleus (SCN) were used to determine whether the same neural substrate may underlie the circadian rhythms and the ultradian modulation of wheel-running activity in these rats. Whereas sham lesions had little or no effect on the wheel-running activity pattern, complete SCN lesions resulted in a complete loss of circadian and ultradian activity components under free-running or 12:12 h light-dark cycle (12:12 LD) conditions. Ultradian and circadian activity components were still present after partial SCN lesions. Periodogram analysis for any given animal revealed that the ultradian periods were always submultiples of the entrained or free-running circadian period. Furthermore there was a high correlation between the amplitudes of circadian and ultradian spectral estimates, but with a different slope in males and females. These results indicate that in LEW/Ztm rats the SCN contributes to the control of both the circadian wheel-running rhythm and the trimodal ultradian modulation of that behavior.Item Open Access Inhibitor of protein synthesis phase shifts a circadian pacemaker in mammalian SCN(1988) Inouye, Shin-Ichi T.; Takahashi, Joseph S.; Wollnik, Franziska; Turek, Fred W.The suprachiasmatic nucleus (SCN) of the hypothalamus contains a circadian pacemaker that regulates many circadian rhythms in mammals. Experimental work in microorganisms and invertebrates suggests that protein synthesis is required for the function of the circadian oscillator, and recent experiments in golden hamsters suggest an acute inhibition of protein synthesis can induce phase shifts in a mammalian circadian pacemaker. To determine whether protein synthesis in the SCN region is involved in the generation of circadian rhythms in mammals, a protein synthesis inhibitor, anisomycin, was microinjected into the SCN region, and the effect on the circadian rhythm of locomotor activity of hamsters was measured. A single injection of anisomycin into the SCN region induced phase shifts in the circadian activity rhythm that varied systematically as a function of the phase of injection within the circadian cycle. These results suggest that protein synthesis may be involved in the generation of circadian rhythms in mammals and that the anatomic site of action of anisomycin is within the hypothalamic suprachiasmatic region.Item Open Access Estrous correlated modulations of circadian and ultradian wheel-running activity rhythms in LEW/Ztm rats(1988) Wollnik, Franziska; Turek, Fred W.Estrogen treatment alters the expression of ultradian activity rhythms in male and female LEW/Ztm rats. This finding raises the possibility that the expression of ultradian rhythms may vary on different days of the estrous cycle. To test this hypothesis, we recorded the circadian and ultradian wheel-running activity rhythms of entrained (LD 12:12) and free-running sexually mature LEW/Ztm females during their 4- or 5-day estrous cycle. The mean daily activity, the duration of activity, the circadian period of activity, and the occurrence of ultradian rhythms differed significantly among the days of the estrous cycle. In LD 12:12, the phase angle difference between the beginning of activity and light offset varied reliably in 5-day cycling animals. The highest daily mean of activity, the longest duration, and the shortest circadian period length were observed on the day of estrus in both entrained and free-running animals. The day of estrus was characterized by a constant high level of activity throughout the activity phase, while the days following ovulation showed a bi- or trimodal activity pattern. Power spectrum analysis revealed significant ultradian components for the days of metestrus and diestrus, but only circadian components for the days of proestrus and estrus. These results were interpreted as indicating that endogenous changes in circulating hormone levels can induce changes in the ultradian and circadian patterns of wheel-running activity in LEW/Ztm rats.Item Open Access Effects of complete and partial SCN lesions on ultradian and circadian locomotor activity rhythms in LEW/Ztm rats : [abstract](1987) Wollnik, Franziska; Turek, Fred W.Both circadian end ultradian rhythms in locomotor activity have been observed in laboratory rats. However, while the neural pacemaker involved in the regulation of the circadian activity rhythm (as well as many other rodent circadian rhythms) appears to be located in the suprachiasmatic nuclei (SCN), the neural basis for the generation of behavioral ultradian rhythms remains unclear, Complete and partial lesions of the SCN were used to determine if the same neural substitute may underlie both circadian and ultradian rhythms in the wheel-running activity of LEW/Ztm rats.