Light-dependent and light-independent estrous cycles and locomotor activity rhythms in rats regulating their cage illumination
Titel:
Light-dependent and light-independent estrous cycles and locomotor activity rhythms in rats regulating their cage illumination
Auteur:
Inoue, Shojiro
Verschenen in:
Biological rhythm research
Paginering:
Jaargang 12 (1981) nr. 2 pagina's 141-160
Jaar:
1981-05
Inhoud:
Female rats were individually housed in a cage placed inside a small light-proof chamber. They were allowed to switch on and off the ceiling lamp of the chamber by pressing a lever. Adult rats, raised under LD 12:12 and exhibiting regular 4-day estrous cycles, developed persistent estrus during a 60-day stay in this cage, where self-selected LD alternations were quite irregular depending on animals. Female rats, born and raised under irregular LD cycles controlled by their mother and isolated in such a cage, also produced irregular LD cycles but their extrous cycles repeated regularly. Mating, pregnancy, parturition and lactation took place normally. Their locomotor activity exhibited an ultradian rhythmicity. These rats demonstrated very regular 4-day estrous cycles and 24-h locomotor activity rhythms, when they were transferred to the LD 12:12 environment. Female rats, either born and raised under the illumination control by their mother and by themselves or raised under LD 12:12, developed persistent estrus, if they were housed in a light-proof chamber in which the ceiling lamp was switched on and off unpredictably by a certain rat in a remote separate cage. From these results, it is suggested that the clock mechanism involved in the regulation of the estrous cycle might function independently from the environmental LD cycles unless it is irreversibly entrained by the 24-h LD cycles or disturbed by unpredictably irregular LD alternations. The ultradian pattern of the locomotor activity rhythm might also differentiate and become well-organized into a circadian type after the exposure of the 24-h environmental time cues.
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