Effect of surgical or photoperiodic castration, testosterone replacement or pinealectomy on male hamster running rhythmicity

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

doi:10.1016/0031-9384(81)90106-2

Cited by 89 publications

(51 citation statements)

References 14 publications

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“…, testicular atrophy) during prolonged exposure to a short light-dark cycle [15] . Furthermore, exogenous testosterone was reported to restore running onset precision in hamsters [35). Studies involving castration and testosterone replacement of male LEW/Ztrn rats under continuous light conditions, where the activity rhythms are not entrained to any lighting regime and therefore display their spontaneous periods, are needed to investigate the testosterone dependent changes in the activity pattern of this strain.…”

Section: Discussionmentioning

confidence: 99%

Effects of adult or perinatal hormonal environment on ultradian rhythms in locomotor activity of laboratory LEW/Ztm rats

Wollnik

Döhler

1986

Physiology & Behavior

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. Effects of adult or perinatal hormonal environment on ultradian rhythms in locomotor activity of laboratory LEWIZtm rats. PHYSIOL BEHA V 38(2) [229][230][231][232][233][234][235][236][237][238][239][240] 1986.-Four experiments were performed with male and female rats of the inbred strain LEW/Ztm maintained under a light-dark schedule of 12: 12 hours. The animals were subject to castration CGOX) or ovariectomy (OVX), estradiol 17J3-implantation (E2-capsules), and perinatal hormonal treatments with testosterone propionate (TP) aod an androgen antagonist (cyproterone acetate, CA). Results indicated a difference in the locomotor activity pattern between the two sexes as a result of the endogenous estradiol levels of the adult animals. The activity pall ern of male LEW rats was characterized by ultradian rhythms of 4 and 4.8 hr periods. The female LEW rats, on the other hand, generally exhibited a clear circadian activity pattern and no uttradian activity rhythms. Following ovariectomy, each of the females showed distinct ultradian rhythms. These disappeared after E2-implantation. Castration of adult males had no effect on the ultradian activity pattern. Implantation of E2-capsules resulted in a marked decrease of the ultradian activity components. Perinatal treatment of the males with an androgen antagonist (CA) did not appear to effect ultradian rhythms during adulthood. Females treated perinatally with testosterone showed a significant increase in the ultradian activity components. This effect is assumed to be due to low estrogen levels in these animals during adulthood. Our study supports the assumption that ultradian rhythms are a result of changes in I he phase relationships between several circadian oscillators. The synchrony of these oscillations seems to be facilitated by estradiol. Ultradian rhythmsLocomotor activity Gonadectomy Brain differentiation Laboratory rat SEVERAL weU-known phenomena of circadian rhythms in mammals can be explained by the model of the circadian system as a composite of multiple, highly ordered oscillators [40][41][42]46]located in or close to the suprachiasmatic nuclei in the hypothalamus [47]. The origin of similar temporal variations on a smaUer time scale, caUed ultradian or short-term rhythms, remains unclear [11]. Ultradian rhythms in locomotor activity are known to exist in laboratory rats [8, 9, 2~30, 49], however, attracting much less attention than circadian rhythms.A recent study of LEW/Ztm rats has shown that ultradian rhythms of 4 and 4.8 hr periods are geneticaUy fixed in this Estradiol Testosterone inbred strain (9]. The persistence of these ultradian rhythms foUowing the disruption of circadian organization under continuous light supported the assumption that the activity rhythms of this strain are caused by an independent ultradian oscillator [9]. Alternatively, the persistence of ultradian rhythms can be explained by changes in the phase relationships between several circadian oscillators [46). The ultradian rhythms of the inbred strain LEW/Ztm are sex-specific, ...

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Section: Discussionmentioning

confidence: 99%

Effects of adult or perinatal hormonal environment on ultradian rhythms in locomotor activity of laboratory LEW/Ztm rats

Wollnik

Döhler

1986

Physiology & Behavior

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“…Extended exposure to short day lengths induces a decrease in testicular size and a decline in plasma testosterone concentrations in male hamsters (Ellis and Turek, 1983). Following testicular regression (or after castration), there is an increase in lability of activity onset, an expansion of the daily activity duration, with a decrease in wheel revolutions per cycle; testosterone replacement prevents these changes (Morin and Cummings, 1981). Testosterone may act through SCN androgen receptors.…”

Section: Endocrine Influences On the Circadian Systemmentioning

confidence: 99%

The regulation of neuroendocrine function: Timing is everything

Kriegsfeld

Silver

2006

Hormones and Behavior

130

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Hormone secretion is highly organized temporally, achieving optimal biological functioning and health. The master clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus coordinates the timing of circadian rhythms, including daily control of hormone secretion. In the brain, the SCN drives hormone secretion. In some instances, SCN neurons make direct synaptic connections with neurosecretory neurons. In other instances, SCN signals set the phase of "clock genes" that regulate circadian function at the cellular level within neurosecretory cells. The protein products of these clock genes can also exert direct transcriptional control over neuroendocrine releasing factors. Clock genes and proteins are also expressed in peripheral endocrine organs providing additional modes of temporal control. Finally, the SCN signals endocrine glands via the autonomic nervous system, allowing for rapid regulation via multisynaptic pathways. Thus, the circadian system achieves temporal regulation of endocrine function by a combination of genetic, cellular, and neural regulatory mechanisms to ensure that each response occurs in its correct temporal niche. The availability of tools to assess the phase of molecular/cellular clocks and of powerful tract tracing methods to assess connections between "clock cells" and their targets provides an opportunity to examine circadian-controlled aspects of neurosecretion, in the search for general principles by which the endocrine system is organized. KeywordsCircadian; Diurnal; Endocrinel; Neurosecretion; Clock genes; Suprachiasmatic Circadian aspects of reproductionThe importance of circadian (about a day) timing in hormone production/secretion has been known since the 1950s when Everett and Sawyer determined that a stimulatory signal occurring during a narrow temporal window on the afternoon of proestrus is necessary for induction of ovulation later that night (Everett and Sawyer, 1950). Such close temporal organization is important for successful reproduction, as numerous hormone-dependent behavioral and physiological processes must be coordinated. If optimal temporal relationships are disrupted, pronounced deficits in fertility can result. For example, ovulation, behavioral estrus, fertilization, and pregnancy maintenance require a specific

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“…Investigators have employed very different markers even in the case of the onset of activity in standard activity rhythms. Often, these are defined in a somewhat arbitrary manner, e.g., by selecting the first 5min bin in which activity attained 20% of maximal activity in a given cycle (Scarbrough and Turek, 1996) or by estimating the fifth percentile of the number of minutes with activity during 15h of a daily cycle (Morin and Cummings, 1981). Such approaches involve some sort of smoothing or bandpass filtering to reduce unwanted variance.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, increased variance of the overt rhythm does not necessarily reflect increased variance of the pacemaker. Different phase definitions applied to the same overt rhythm yield different standard deviations (Morin and Cummings, 1981).…”

Section: Introductionmentioning

confidence: 99%

The Precision of Circadian Clocks: Assessment and Analysis in Syrian Hamsters

Daan

Oklejewicz

2003

Chronobiology International

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Locomotor activity recordings of Syrian hamsters were systematically analyzed to estimate the precision of the overt circadian activity rhythm in constant darkness. Phase variation, i.e., the standard deviation of phase markers around the regression line, varied with the definition of phase. Smallest phase variation was found in the onset of wheel running activity defined by 1h running means of the raw data. Both lower and higher degrees of smoothing lead to decreased precision measured in the overt rhythm. With passive infrared recordings, the midpoint of activity defined by 3h running means was the least variable. This demonstrates that the choice of phase marker should vary between recording methods. Phase variation decreased with increasing activity and was larger in females than in males. By calculating the average cycle variation and serial covariance of consecutive cycles, we estimated the contribution of 'clock' and 'nonclock' related processes to the overt rhythm variability. Variance in precision between phase markers could be shown to be attributable mainly to nonclock processes. Variance in pacemaker cycle length appeared reduced in wheel running activity records compared with passive infrared sensing records, suggesting feedback from running activity onto pacemaker function.

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Effect of surgical or photoperiodic castration, testosterone replacement or pinealectomy on male hamster running rhythmicity

Cited by 89 publications

References 14 publications

Effects of adult or perinatal hormonal environment on ultradian rhythms in locomotor activity of laboratory LEW/Ztm rats

Effects of adult or perinatal hormonal environment on ultradian rhythms in locomotor activity of laboratory LEW/Ztm rats

The regulation of neuroendocrine function: Timing is everything

The Precision of Circadian Clocks: Assessment and Analysis in Syrian Hamsters

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