Effect of ovariectomy and estradiol on unity of female rat circadian rhythms.
Sixteen rats were ovariectomized and given either a 1-cm implant of crystalline estradiol-17 beta (eight rats) or an empty implant (eight rats). A further six rats were sham ovariectomized and given empty implants, and eight rats were left unoperated. The rats were exposed to 70 days of constant dim light (LL) with a maximum illumination level of 20 lx, and circadian running and drinking rhythms were monitored. In LL, both the running and drinking activity rhythms of the ovariectomized, blank-implanted rats became markedly disrupted, whereas unoperated and sham-operated rats maintained unified rhythms. Estradiol-implanted rats developed fewer rhythm desynchronies, and the majority displayed a single band of free-running activity. Rather than being arrhythmic, the activity of the LL-exposed ovariectomized rats appeared to contain several free-running components. Thus these data are consistent with the concept of a multioscillatory basis to the circadian system and support a role for the ovary and its hormone estradiol in the maintenance of coherence between component oscillators.
Thomas
E M
EM
Department of Physiology, Monash University, Clayton, Victoria, Australia.
Armstrong
S M
SM
D000204:Activity Cycles / Q000187:drug effects / Q000528:radiation effects; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002940:Circadian Rhythm / Q000187:drug effects* / Q000528:radiation effects; D004343:Drug Implants; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D008027:Light; D010052:Ovariectomy; D011863:Radioimmunoassay; D051381:Rats; D011919:Rats, Inbred Strains
D004343:Drug Implants; D004958:Estradiol