Splitting of wheelrunning rhythms by castrated or steroid treated male and female hamsters

Morin, L.P.; Cummings, L.A.

doi:10.1016/0031-9384(82)90236-0

Cited by 62 publications

(35 citation statements)

References 25 publications

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“…Estradiol also modulates overall locomotor activity levels in males (72,73). Treatment with estradiol benzoate reduces the number of rhythm desynchronies in ovariectomized female hamsters housed in constant light, but no effect of either testosterone or estradiol benzoate is seen in males (75,76). The effects of activity on circadian rhythmicity are well known (77), and it is likely that a component of the estrogenic effect on circadian timing is a result of indirect activity effects that can then modulate rhythmicity.…”

Section: Ovarian Hormones and Circadian Behaviormentioning

confidence: 99%

Minireview: The Neuroendocrinology of the Suprachiasmatic Nucleus as a Conductor of Body Time in Mammals

Karatsoreos

Silver

2007

Endocrinology

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Circadian rhythms in physiology and behavior are regulated by a master clock resident in the suprachiasmatic nucleus (SCN) of the hypothalamus, and dysfunctions in the circadian system can lead to serious health effects. This paper reviews the organization of the SCN as the brain clock, how it regulates gonadal hormone secretion, and how androgens modulate aspects of circadian behavior known to be regulated by the SCN. We show that androgen receptors are restricted to a core SCN region that receives photic input as well as afferents from arousal systems in the brain. We suggest that androgens modulate circadian behavior directly via actions on the SCN and that both androgens and estrogens modulate circadian rhythms through an indirect route, by affecting overall activity and arousal levels. Thus, this system has multiple levels of regulation; the SCN regulates circadian rhythms in gonadal hormone secretion, and hormones feed back to influence SCN functions.For optimal function, organisms and cells must locate and operate in a defined temporal and spatial niche. The need for resource partitioning is obvious in the spatial domain and is also important in the temporal domain. The daily rising and setting of the sun provides a predictable environmental time cue to which organisms are sensitive. In mammals, a master circadian clock located in the suprachiasmatic nucleus (SCN) ensures that peripheral clocks throughout the brain and body function in the appropriate phase. Entrainment (synchronization to the environment) in mammalian systems involves the resetting of this master clock, which then communicates timing information to the rest of the body. In the absence of environmental cues, the internal clock runs at its endogenous, free-running period. This system permits the prediction of environmental changes while maintaining plastic responses to changes in the environment. SCN as Brain ClockEvidence that the SCN is the locus of a master circadian clock in mammals has been gathered over many years from many labs and entails methodologically distinct experimental paradigms with converging lines of evidence (1, 2). Briefly, lesions of the SCN result in a loss of all circadian rhythmicity in behavior and physiology, including hormone secretion. The SCN expresses rhythmic electrical and metabolic activity, even when placed in a dish in isolation from the rest of the brain (3, 4). After creation of a hypothalamic island containing the SCN, rhythmic electrical activity continues within the island (5), and hamsters bearing such hypothalamic islands continue to show rhythmic locomotor activity although the gonadal regression response to long-term constant darkness is lost (6). Transplantation of fetal hypothalamic tissue containing the SCN into the third ventricle of an SCN-lesioned animal restores circadian locomotor rhythms with a period reflecting that of the donor animal, but again, the gonadal regression response to constant darkness is lost (7,8). Interestingly, rhythms in hormone secretion are not restored by ...

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Section: Ovarian Hormones and Circadian Behaviormentioning

confidence: 99%

Minireview: The Neuroendocrinology of the Suprachiasmatic Nucleus as a Conductor of Body Time in Mammals

Karatsoreos

Silver

2007

Endocrinology

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“…For example, the circadian rhythm of activity in rodent changes significantly during the 4-5 day estrous cycle [2]. In hamsters, degus and rats, gonadectomy causes a significant change in the behavioral patterns, which is reversed by gonadal steroid hormone replacement [3][4][5].The core clock mechanism in mammals is based on a transcriptional translational feedback loop involving the Period (Per) and Cryptochrome (Cry) genes as negative elements, the basic helix-loop-helix Per-Arnt-Sim (PAS) transcription factors CLOCK and BMAL1 as positive components [6], and a range of auxiliary loops for stabilization [6,7]. Recently, in rodent, it has been demonstrated that the timing of clock gene expression in the brain and periphery is affected by estrous cycle stage and ovarian steroid hormone depletion following ovariectomy [8].…”

mentioning

confidence: 99%

Influence of menstrual cycle on the expression of clock genes in peripheral blood mononuclear cells in Macaca fascicularis

Miao

et al. 2015

European Journal of Obstetrics & Gynecology and Reproductiv

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“…In Orchx rats with testosterone supplement, 1 cm of the silastic tube (inner diameter 1.56 mm, outer diameter 3.15 mm; Dow Corning Corporation, Midland, MI, USA) containing 3 mg testosterone (Sigma Chemical Co, St Louis, MO, USA) was simultaneously implanted through a small incision in the skin over the back of anaesthetized rats, according to the method of Morin and Cummings. 18 Changes in body weight and daily food intake were observed for three weeks after the operation. Following three-week observation, all animals were killed and a piece of RWAT was immediately dissected and used for the determination of ob gene mRNA expression.…”

Section: Animalsmentioning

confidence: 99%

Orchiectomy and response to testosterone in the development of obesity in young Otsuka-Long-Evans-Tokushima Fatty (OLETF) rats

et al. 1998

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OBJECTIVE: Withdrawal of testosterone prevents the development of hyperglycaemia in male Otsuka-Long-EvansTokushima Fatty (OLETF) rats, a model of non-insulin-dependent diabetes mellitus (NIDDM), but the exact mechanism has not been established. The present studies were undertaken to examine a possible role of testosterone in the development of obesity in young OLETF rats who have not shown marked hyperphagia. METHODS: Body weight, food intake and circulating concentrations of metabolic factors including immunoreactive leptin (IRL) were measured at ®ve weeks of age in young male OLETF rats and their lean controls, Long-EvansTokushima-Otsuka (LETO) rats. At six weeks of age, both LETO and OLETF rats were bilaterally orchiectomized (Orchx) and half of each group implanted with a silastic tube containing testosterone. After a three week observation period, all animals were killed and circulating concentrations of metabolic factors and the ob gene expression in retroperitoneal white adipose tissues were measured. RESULTS: Body weight and 24 h food intake were already increased in OLETF rats at ®ve weeks of age. Serum testosterone concentrations were signi®cantly lower in OLETF rats than in LETO rats. Expression of the ob gene was signi®cantly decreased in the retroperitoneal white adipose tissue of OLETF rats, and their serum IRL concentrations were lower. Food intake and body weight gain for three weeks after the operation were signi®cantly lower in the Orchx group of OLETF rats than in the sham-operated group. Hyperglycaemia, accompanied by hyperinsulinaemia, was attenuated by orchiectomy in OLETF rats. Circulating IRL concentrations were signi®cantly higher in OLETF rats than in LETO rats and decreased by orchiectomy. Testosterone supplement reversed all of the changes caused by orchiectomy in OLETF rats. In contrast, the changes, which were observed after orchiectomy in OLETF rats, were not obvious in LETO rats. CONCLUSION: The present data indicate that testosterone plays a role in the development of obesity and NIDDM in young OLETF rats, but that changes of leptin production in white adipose tissue may not be important in the development of obesity in young OLETF rats.

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Splitting of wheelrunning rhythms by castrated or steroid treated male and female hamsters

Cited by 62 publications

References 25 publications

Minireview: The Neuroendocrinology of the Suprachiasmatic Nucleus as a Conductor of Body Time in Mammals

Minireview: The Neuroendocrinology of the Suprachiasmatic Nucleus as a Conductor of Body Time in Mammals

Influence of menstrual cycle on the expression of clock genes in peripheral blood mononuclear cells in Macaca fascicularis

Orchiectomy and response to testosterone in the development of obesity in young Otsuka-Long-Evans-Tokushima Fatty (OLETF) rats

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