Affective responses to changes in day length in Siberian hamsters (Phodopus sungorus)

Individuals of many nontropical rodent species display reproductive, immunological, and somatic responses to day length. In general, short day (SD) lengths inhibit reproduction and enhance immune function in the laboratory when all other conditions are held constant. Most studies to date have focused on seasonal variation in immune function in adulthood. However, perinatal photoperiods also communicate critical day length information and serve to establish a developmental trajectory appropriate for the time of year. Nontropical rodents born early in the breeding season undergo rapid reproductive development, presumably to promote mating success during their first reproductive season. Rodents born late in the breeding season suspend somatic growth and puberty until the following vernal breeding season. We tested the hypothesis that perinatal day lengths have similar enduring effects on the immune system of rodents. Siberian hamsters ( Phodopus sungorus) were maintained prenatally and until weaning (21 days) in either SDs (8 h light:16 h dark) or long days (LD) (16 h light:8 h dark), then they were weaned into either the opposite photoperiod or maintained in their natal photoperiod, forming four groups (LD-LD, LD-SD, SD-LD, and SD-SD). After 8-wk in these conditions, cell-mediated immune activity was compared among groups. SD-SD hamsters of both sexes enhanced immune function relative to all other groups. The reproductive effects of perinatal photoperiod were not evident by the end of the experiment; circulating testosterone and cortisol sampled at the end of the experiment reflected the postweaning, but not the perinatal photoperiod. This experiment demonstrates long-lasting organizational effects of perinatal photoperiod on the rodent immune system and indicates that photoperiod-induced changes in the immune system are dissociable from changes in the reproductive system.

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MT1 Melatonin Receptors Mediate Somatic, Behavioral, and Reproductive Neuroendocrine Responses to Photoperiod and Melatonin in Siberian Hamsters (Phodopus sungorus)

Endocrinology ◽

10.1210/en.2009-0710 ◽

2010 ◽

Vol 151 (2) ◽

pp. 714-721 ◽

Cited By ~ 29

Author(s):

Brian J. Prendergast

Keyword(s):

Reproductive Function ◽

Melatonin Receptors ◽

Day Length ◽

Phodopus Sungorus ◽

Receptor Subtypes ◽

Gonadotropin Secretion ◽

Siberian Hamsters ◽

The Central Nervous System ◽

Necessary And Sufficient ◽

And Behavior

Environmental day length drives nocturnal pineal melatonin secretion, which in turn generates or entrains seasonal cycles of physiology, reproduction, and behavior. In mammals, melatonin (MEL) binds to a number of receptor subtypes including high-affinity (MT1 and MT2) and low-affinity (MT3, nuclear orphan receptors) binding sites, which are distributed throughout the central nervous system and periphery. The MEL receptors that mediate photoperiodic reproductive and behavioral responses to MEL have not been identified in a reproductively photoperiodic species. Here I tested the hypothesis that MT1 receptors are necessary and sufficient to engage photoperiodic responses by challenging male Siberian hamsters (Phodopus sungorus), a species that does not express functional MT2 receptors, with ramelteon (RAM), a specific MT1/MT2 receptor agonist. In hamsters housed in a long-day photoperiod, late-afternoon RAM treatment inhibited gonadotropin secretion, induced gonadal regression, and suppressed food intake and body mass, mimicking effects of MEL. In addition, chronic (24 h/d) RAM infusions were sufficient to obscure endogenous MEL signaling, and these treatments attenuated gonadal regression in short days. Together, the outcomes indicate that signaling at the MT1 receptor is sufficient and necessary to mediate the effects of photoperiod-driven changes in MEL on behavior and reproductive function in a reproductively photoperiodic mammal.

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Photoperiod-dependent modulation of anti-Müllerian hormone in female Siberian hamsters, Phodopus sungorus

Reproduction ◽

10.1530/rep-07-0423 ◽

2008 ◽

Vol 135 (3) ◽

pp. 335-342 ◽

Cited By ~ 19

Author(s):

Esther W Kabithe ◽

Ned J Place

Keyword(s):

Granulosa Cells ◽

Expression Patterns ◽

Follicular Development ◽

Day Length ◽

Phodopus Sungorus ◽

Reproductive Aging ◽

Primordial Follicles ◽

Short Day ◽

Siberian Hamsters ◽

Secondary Stage

Fertility and fecundity decline with advancing age in female mammals, but reproductive aging was decelerated in Siberian hamsters (Phodopus sungorus) raised in a short-day (SD) photoperiod. Litter success was significantly improved in older hamsters when reared in SD and the number of primordial follicles was twice that of females held in long days (LD). Because anti-Müllerian hormone (AMH) appears to inhibit the recruitment of primordial follicles in mice, we sought to determine whether the expression patterns of AMH differ in the ovaries and serum of hamsters raised in SD versus LD. Ovaries of SD female hamsters are characterized by a paucity of follicular development beyond the secondary stage and are endowed with an abundance of large eosinophilic cells, which may derive from granulosa cells of oocyte-depleted follicles. In ovaries from 10-week-old SD hamsters, we found that the so-called ‘hypertrophied granulosa cells’ were immunoreactive for AMH, as were granulosa cells within healthy-appearing primary and secondary follicles. Conversely, ovaries from age-matched LD animals lack the highly eosinophilic cells present in SD ovaries. Therefore, AMH staining in LD was limited to primary and secondary follicles that are comparable in number to those found in SD ovaries. The substantially greater AMH expression in SD ovaries probably reflects the abundance of hypertrophied granulosa cells in SD ovaries and their relative absence in LD ovaries. The modulation of ovarian AMH by day length is a strong mechanistic candidate for the preservation of primordial follicles in female hamsters raised in a SD photoperiod.

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Sleep deprivation attenuates endotoxin-induced cytokine gene expression independent of day length and circulating cortisol in male Siberian hamsters (Phodopus sungorus)

Journal of Experimental Biology ◽

10.1242/jeb.083832 ◽

2013 ◽

Vol 216 (14) ◽

pp. 2581-2586 ◽

Cited By ~ 10

Author(s):

N. T. Ashley ◽

J. C. Walton ◽

A. Haim ◽

N. Zhang ◽

L. A. Prince ◽

...

Keyword(s):

Gene Expression ◽

Sleep Deprivation ◽

Day Length ◽

Cytokine Gene Expression ◽

Phodopus Sungorus ◽

Cytokine Gene ◽

Siberian Hamsters

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Housing condition alters immunological and reproductive responses to day length in Siberian hamsters (Phodopus sungorus)

Hormones and Behavior ◽

10.1016/j.yhbeh.2007.05.001 ◽

2007 ◽

Vol 52 (2) ◽

pp. 261-266 ◽

Cited By ~ 12

Author(s):

Zachary M. Weil ◽

Joanna L. Workman ◽

Randy J. Nelson

Keyword(s):

Housing Condition ◽

Day Length ◽

Phodopus Sungorus ◽

Siberian Hamsters

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Social Cues Attenuate Photoresponsiveness of the Male Reproductive System in Siberian Hamsters (Phodopus sungorus)

Journal of Biological Rhythms ◽

10.1177/074873099129000443 ◽

1999 ◽

Vol 14 (1) ◽

pp. 54-61 ◽

Cited By ~ 16

Author(s):

Carol D. Hegstrom ◽

S. Marc Breedlove

Keyword(s):

Reproductive System ◽

Social Cues ◽

Male Reproductive System ◽

Phodopus Sungorus ◽

Siberian Hamsters

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Energy intake and fur in summer- and winter-acclimated Siberian hamsters (Phodopus sungorus)

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.2001.281.2.r519 ◽

2001 ◽

Vol 281 (2) ◽

pp. R519-R527 ◽

Cited By ~ 9

Author(s):

Alexander S. Kauffman ◽

Alessandra Cabrera ◽

Irving Zucker

Keyword(s):

Food Intake ◽

Energy Intake ◽

Ventral Surface ◽

Phodopus Sungorus ◽

Ambient Temperatures ◽

Siberian Hamsters ◽

Daily Food ◽

Brown Adipose ◽

Wide Range ◽

The Impact

Few studies have directly addressed the impact of fur on seasonal changes in energy intake. The daily food intake of Siberian hamsters ( Phodopus sungorus) was measured under simulated summer and winter conditions in intact animals and those with varying amounts of pelage removed. Energy intake increased up to 44% above baseline control values for approximately 2–3 wk after complete shaving. Increases in food intake varied with condition and were greater in hamsters housed in short than long day lengths and at low (5°C) than moderate (23°C) ambient temperatures. Removal of 8 cm2 of dorsal fur, equivalent to 30% of the total dorsal fur surface, increased food intake, but removal of 4 cm2 had no effect. An 8-cm2 fur extirpation from the ventral surface did not increase food consumption. Food intake was not influenced differentially by fur removal from above brown adipose tissue hot spots. Fur plays a greater role in energy balance in winter- than summer-acclimated hamsters and conserves energy under a wide range of environmental conditions.

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