Long-Term Reproductive Effects of a Single Long Day in the Siberian Hamster (Phodopus sungorus

Finley, Cynthia M.; Gorman, Michael R.; Tuthill, Christiana R.; Zucker, Irving H.

doi:10.1177/074873049501000103

Cited by 19 publications

(12 citation statements)

References 16 publications

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“…Our results extend earlier findings that Siberian hamsters are highly responsive to changes in day length near the time of weaning (Elliott and Goldman, 1989;Finley et al, 1995;Spears et al, 1990;Whaling et al, 1993). They support the conclusion that once the interval timer is triggered by several weeks of short day lengths, elimination of melatonin signals (experiment 1) has little effect on interval timing (Anchordoquy and Lynch, 2000).…”

Section: Discussionsupporting

confidence: 90%

Interval Timer Control of Puberty in Photoinhibited Siberian Hamsters

et al. 2006

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Puberty, which is markedly delayed in male Siberian hamsters (Phodopus sungorus) born into short day lengths, is controlled by an interval timer regulated by the duration of nocturnal melatonin secretion. Properties of the interval timer were assessed by perturbing normal patterns of melatonin secretion in males gestated and maintained thereafter in 1 of 2 short day lengths, 10 h light/day (10 L) or 12L. Melatonin secretion of short-day hamsters was suppressed by constant light treatment or modified by daily injection of propranolol to mimic nocturnal melatonin durations typical of long-day hamsters. Constant light treatment during weeks 3 to 5 induced early incomplete gonadal growth in 12L but not 10 L hamsters but did not affect late onset of gonadal development indicative of puberty in either photoperiod. Propranolol treatment during postnatal weeks 3 to 5 induced transient growth of the testes and ultimately delayed the timing of puberty by 3 weeks. Similar treatments between weeks 5 and 7 or on alternate weeks for 24 weeks did not affect the interval timer. The first 2 weeks after weaning may constitute a critical period during which the interval timer is highly responsive to photoperiod. Alternatively, the hamsters' photoperiodic history rather than age or developmental stage may be the critical variable. The interpolation of long-day melatonin signals at the time of weaning does not appear to reset the interval timer to its zero position but may reduce timer responsiveness to long-day melatonin signals several weeks later.

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Section: Discussionsupporting

confidence: 90%

Interval Timer Control of Puberty in Photoinhibited Siberian Hamsters

et al. 2006

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“…This result may point to an immediate response to LD, as in the ‘first‐day release’ model in which luteinizing hormone and follicle‐stimulating hormone secretion occur on the first day after release to long photoperiods (Nicholls et al. , 1983) or, as observed in Siberian hamsters, a single long‐day exposure prevented testicular regression in a subsequent short photoperiod (Finley et al. , 1995).…”

Section: Discussionmentioning

confidence: 97%

Day‐length encoding through tonic photic effects in the retinorecipient SCN region

Yan

Silver

2008

Eur J of Neuroscience

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The circadian clock in the suprachiasmatic nucleus (SCN) plays a critical role in seasonal processes by sensing ambient photoperiod. To explore how it measures daylength, we assessed the state of SCN oscillators using markers for neuronal activity (c-FOS) and the clock protein (PER1) in Syrian hamsters housed in long (LD, 16:8hr light:dark) versus short days (SD, 8:16hr light:dark). During SD, there was no detectable phase dispersion across the rostro-caudal extent of the nucleus. In contrast, during LD, rhythms in the caudal SCN phase led those in the mid-and rostral SCN by 4-8 h and 8-12 h, respectively. Importantly, some neurons in the retinorecipient core SCN were unique in that they were FOS-positive during the dark phase in LD, but not SD. Transfer of LD animals to constant darkness or skeleton photoperiod revealed that dark phase FOS expression depends on tonic light exposure rather than on intrinsic clock properties. By transferring animals from SD to LD, we next discovered that there are two separate populations of SCN cells one responding to acute and the other to tonic light exposure. The results suggest that the SCN's seasonal encoding of day-length entails reorganization of its constituent oscillators by a subgroup of neurons in the SCN core that respond to tonic photic cues.

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“…In the Japanese quail, a single long day stimulates LH release [46]. A single long day also affects phenotypic indicators of sexual maturation in at the photoperiodic Siberian hamster [25]. In the threespine stickleback, LH expression rises above baseline after 5–10 long days but, given the effects of a single long day on quail and hamsters, the later expression in LH does not necessarily mean that 5–10 long days are necessary for LHβ expression or to commit stickleback to sexual maturation.…”

Section: Discussionmentioning

confidence: 99%

Conservation of the photoperiodic neuroendocrine axis among vertebrates: Evidence from the teleost fish, Gasterosteus aculeatus

O’Brien

Bourdo

Bradshaw

et al. 2012

General and Comparative Endocrinology

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Photoperiod, or length of day, has a predictable annual cycle, making it an important cue for the timing of seasonal behavior and development in many organisms. Photoperiod is widely used among temperate and polar animals to regulate the timing of sexual maturation. The proper sensing and interpretation of photoperiod can be tightly tied to an organism’s overall fitness. In photoperiodic mammals and birds the thyroid hormone pathway initiates sexual maturation, but the degree to which this pathway is conserved across other vertebrates is not well known. We use the threespine stickleback Gasterosteus aculeatus, as a representative teleost to quantify the photoperiodic response of key genes in the thyroid hormone pathway under controlled laboratory conditions. We find that the photoperiodic responses of the hormones are largely consistent amongst multiple populations, although differences suggest physiological adaptation to various climates. We conclude that the thyroid hormone pathway initiates sexual maturation in response to photoperiod in G. aculeatus, and our results show that more components of this pathway are conserved among mammals, birds, and teleost fish than was previously known. However, additional endocrinology, cell biology and molecular research will be required to define precisely which aspects of the pathway are conserved across vertebrates.

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Long-Term Reproductive Effects of a Single Long Day in the Siberian Hamster (Phodopus sungorus

Cited by 19 publications

References 16 publications

Interval Timer Control of Puberty in Photoinhibited Siberian Hamsters

Interval Timer Control of Puberty in Photoinhibited Siberian Hamsters

Day‐length encoding through tonic photic effects in the retinorecipient SCN region

Conservation of the photoperiodic neuroendocrine axis among vertebrates: Evidence from the teleost fish, Gasterosteus aculeatus

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