The influence of 60-minute dark and 60-minute light signals on the circadian caecotrophy rhythm of the rabbit
Titel:
The influence of 60-minute dark and 60-minute light signals on the circadian caecotrophy rhythm of the rabbit
Auteur:
Jilge, Burghart
Verschenen in:
Biological rhythm research
Paginering:
Jaargang 12 (1981) nr. 1 pagina's 41-55
Jaar:
1981-03
Inhoud:
The caecotrophy rhythm of 15 male rabbits was registered continuously for 320 days at 5 different LD schedules (LD 12:12, LL, LD 23:1, LD 11:1 + 11:1, LD 12:12). The results were compared with the preceding experiment of the reverse set-up. The following results were obtained: The caecotrophy rhythm, biphasic during LD 12:12, ran free mono-phasically in all animals. Aftereffects of the preceding LD 12:12 were present for up to 52 days, affecting the length of the free-running period significantly. The insertion of the 60-minute scotoperiod schedule was responded by delay shifts, the signal meeting the free-running rhythm during the early subjective night, and by advance shifts, when the signal occurred during the late subjective night. Eight animals did entrain with the 60-minute scotoperiod. The average phase angle difference was negative; both the interindividual and intra-individual scatters were very high. Seven animals did not entrain with the LD 23:1 but exhibited an oscillatory free-run. During the skeleton scotoperiod only 6 animals showed stable entrainment, 9 animals failed to entrain with this Zeitgeber. The comparison of the phase angles during the 60-minute scoto- and photoperiod experiments, the respective skeleton-photoperiod experiments and the complete LD 12:12 schedules indicates that the phase angle difference becomes more negative at an increasing LD ratio in the rabbit. The results suggest that a sceleton photoperiod is nearly as strong a Zeitgeber as a complete LD 12:12 and that Zeitgeber strength decreases from LD 1:23 to LD 23:1 to LD 11:1 + 11:1. The oscillatory free-run can be explained reasonably on the assumption of a more pronounced delay section of the phase response curve in these rabbits.
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