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Effects of sex, thyro-parathyroidectomy, and light regime on levels and circadian rhythms of wheel-running in rats
Journal article   Peer reviewed

Effects of sex, thyro-parathyroidectomy, and light regime on levels and circadian rhythms of wheel-running in rats

Jonathan Schull, Joe Walker, Kent Fitzgerald, Leena Hiilivirta, Jason Ruckdeschel, Diane Schumacher, Deborah Stanger and Donald L. McEachron
Physiology & behavior, v 46(3), pp 341-346
1989
PMID: 2623053

Abstract

Activity Animal model Bipolar Affective Disorder Circadian rhythms Depression Entrainment Female Free-Run Lighting Male Mania Parathyroidectomy Rats Sex differences Thyro-parathyroidectomy Thyroidectomy Wheel-running
Intact and thyro-parathyroidectomized (TPX) Sprague-Dawley rats of both sexes were observed for 24 days under a 12:12 light:dark cycle (Entrainment), followed by 20 days in constant dim red light (Free-Run). Circadian periods and levels of wheel-running activity were examined. Intact females and TPX males were significantly more active and had significantly shorter free-running circadian periods than intact males, and the effects of TPX in females were different from those in males. Circadian periods in TPX females were slightly, but not significantly, shorter than in intact females, and activity levels in TPX females were nonsignificantly depressed relative to intact females. It was also found that day versus night activity levels differed more in TPX animals than in intact animals, especially during entrainment, suggesting that TPXs may be more sensitive to some effects of light. A number of possible explanations for the effects of TPX are considered, including changes in thyroid and calcitonin levels, interactions with gonadal hormones, and possible developmental effects of thyroid hormones on the circadian system. It is also possible that rhythm changes are secondary to alterations in activity levels. Human manic depressives reportedly have an unusually high incidence of thyroid, parathyroid, and calcium regulation abnormalities, display shortened circadian sleep-wake rhythms and abnormal levels of activity, and may also be hypersensitive to some effects of light; in addition, depression predominates in women, whereas mania predominates in men. The present results suggest that thyroid dysfunction could be partially responsible for the some of these abnormalities, and for sex differences in the manifestations of these disorders.

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Web of Science research areas
Behavioral Sciences
Psychology, Biological
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