Antigonadal Effects of Timed Melatonin Infusion in Pinealectomized Male Djungarian Hamsters (<i>Phodopus sungorus sungorus</i>): Duration is the Critical Parameter*

Carter, Dennis S.; Goldman, Bruce D.

doi:10.1210/endo-113-4-1261

Cited by 402 publications

(239 citation statements)

References 21 publications

Supporting

Mentioning

231

Contrasting

Unclassified

Order By: Relevance

“…3c), and although the tammars had been injected for 15 days before exposure to 15L:9D (Fig. 3b) (Carter & Goldman, 1983a). Similarly, in the tammar, exposure to melatonin for a continuous period longer than 9 h per day may be required to elicit reactivation, since tammars have only been observed to respond to an increase in the dark phase from 15L:9D to 13L:1 ID, or from 15L:9D to 12LT2D, or from melatonin injections 2-5 h before dark given to tammars main¬ tained in 15L:9D.…”

Section: Discussionmentioning

confidence: 98%

Change in duration of elevated concentrations of melatonin is the major factor in photoperiod response of the tammar, Macropus eugenii

McConnell¹,

Tyndale-Biscoe²,

Hinds³

1986

Reproduction

View full text Add to dashboard Cite

Summary. In Exp. 1, 10 quiescent non-lactating tammars were exposed to 15L:9D (Days \p=n-\41to \p=n-\1), 24L 2\p=n-\3h in the morning and all 6 tammars gave birth on Day 31\m=.\2 \m=+-\ 1\m=.\0. A transient pulse of peripheral plasma prolactin (81\m=.\5 \m=+-\31\m=.\0 ng/ml) was detected at dawn during 15L:9D in all 6 tammars but was not observed in any of them 5 days after exposure to 12L:12D. Together these results do not support the time of day hypothesis but indicate that increase in duration of the nocturnal melatonin rise mediates the effects of decreased daylength on reactivation of the corpus luteum, and that the first detectable result of this may be the abolition of a transient prolactin pulse at the end of the dark phase.

show abstract

Section: Discussionmentioning

confidence: 98%

Change in duration of elevated concentrations of melatonin is the major factor in photoperiod response of the tammar, Macropus eugenii

McConnell¹,

Tyndale-Biscoe²,

Hinds³

1986

Reproduction

View full text Add to dashboard Cite

show abstract

“…PINx abolished photoperiodic regulation of most measures of immune function by rendering them in a LD-like, rather than a SD-like, phenotype. PINx likewise renders the reproductive system of Syrian (Hoffman and Reiter, 1965) and Siberian (Carter and Goldman, 1983a) hamsters in a state of permanent reproductive competence (i.e., in the LD-phenotype). This observation suggests that the absence of a melatonin signal is likewise encoded by the immune system either as a LD signal, or as permissive for the expression of prior photoperiod history effects (Anchordoquy and Lynch, 2000;Prendergast et al, 2000Prendergast et al, , 2002a.…”

Section: Discussionmentioning

confidence: 99%

Pineal-dependent and -independent effects of photoperiod on immune function in Siberian hamsters (Phodopus sungorus)

Wen

Dhabhar

Prendergast

2007

Hormones and Behavior

View full text Add to dashboard Cite

Siberian hamsters (Phodopus sungorus) exhibit reproductive and immunological responses to photoperiod. Short (<10-h light/day) days induce gonadal atrophy, increase leukocyte concentrations, and attenuate thermoregulatory and behavioral responses to infection. Whereas hamster reproductive responses to photoperiod are dependent on pineal melatonin secretion, the role of the pineal in short-day induced changes in immune function is not fully understood. To examine this, adult hamsters were pinealectomized (PINx) or sham-PINx, and transferred to short days (9-h light/day; SD) or kept in their natal long-day (15-h light/day; LD) photoperiod. Intact and PINx hamsters housed in LD maintained large testes over the next 12 weeks; sham-PINx hamsters exhibited gonadal regression in SD, and PINx abolished this effect. Among pineal-intact hamsters, blood samples revealed increases in leukocyte, lymphocyte, CD62L+ lymphocyte, and T cell counts in SD relative to LD; PINx did not affect leukocyte numbers in LD hamsters, but abolished the SD increase in these measures. Hamsters were then treated with bacterial lipopolysaccharide (LPS), which induced thermoregulatory (fever), behavioral (anorexia, reductions in nest building), and somatic (weight loss) sickness responses in all groups. Among pineal-intact hamsters, febrile and behavioral responses to LPS were attenuated in SD relative to LD. PINx did not affect sickness responses to LPS in LD hamsters, but abolished the ameliorating effects of SD on behavioral responses to LPS. Surprisingly, PINx failed to abolish the effect of SD on fever. In common with the reproductive system, PINx induces the LD phenotype in most aspects of the immune system. The pineal gland is required for photoperiodic regulation of circulating leukocytes and neural-immune interactions that mediate select aspects of sickness behaviors.

show abstract

“…Additional groups of hamsters were maintained in 15L (LD) or 10L (SD) from birth and at 8-10 weeks of age were pinealectomized (according to procedures described in ref. 13), fitted with s.c. polyethylene cannulae (14), and provided with timed daily 7-h infusions of either Mel (5-methoxytryptamine; 100 ng per infusion) or saline (0.9% NaCl) for 28 consecutive days, after which ETVs were determined.…”

Section: Methodsmentioning

confidence: 99%

Establishment and persistence of photoperiodic memory in hamsters

Prendergast

Gorman

Zucker

2000

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

Long summer days unequivocally stimulate, and short winter days inhibit reproduction in Siberian hamsters. By contrast, intermediate-duration day lengths (12.5-14 h long) either accelerate reproductive development or initiate regression of the reproductive apparatus. Which of these outcomes transpires depends on an animal's photoperiodic history, suggesting that hamsters must encode a representation of prior photoperiods. The duration of nocturnal melatonin secretion is the endocrine representation of day length, but nothing is known about how long it takes to establish photoperiodic histories or how long they endure. Hamsters exposed for 2 or more weeks to long summer day lengths acquired a long-day photoperiodic history that determined subsequent reproductive responses to intermediate-duration day lengths and melatonin signals. The memory for long-day lengths persisted in pinealectomized hamsters for 6.5 weeks, faded significantly after 13 weeks, and was functionally absent after 20 weeks. These findings indicate that hamsters are influenced only by relatively recent day lengths and melatonin signals and ignore earlier ones that might cause them to misinterpret the salience of current day lengths. S easonal breeding is timed so that lactation and subsequent weaning of young coincide with annual peaks in food availability, thereby increasing fitness (1, 2). Variation in day length (DL) is a major environmental cue for phasing reproduction (3); the light-dark cycle entrains an endogenous circadian rhythm of pineal melatonin (Mel) secretion; elevated nightly Mel production is directly proportional to the length of the dark phase and is much longer under short days (SDs) than long days (LDs; typically Ն10 h vs. 5 h per night, respectively; ref. 4). Summer DLs (Ն14 h light per day; 14L) stimulate, and winter days (Յ10L) inhibit reproduction in long-day breeding photoperiodic rodents. Nightly infusions of Mel that match endogenous durations mimic the effects of corresponding DLs on reproductive physiology in pinealectomized rodents deprived of endogenous Mel (5, 6).In photoperiodic history consisting of both long and short DLs, from the preceding summer and winter, respectively. Whether and how such animals are influenced by more recent DLs and ignore earlier ones is unknown. The amount of experience with a particular range of DLs an animal must have before it encodes them as a photoperiodic history also remains to be specified. Herein, we determine how long it takes to establish a long-day photoperiodic history and describe the persistence and eventual decay of this representation of DL over a seasonal time scale. Materials and MethodsAnimals and Procedures. Siberian hamsters (P. sungorus) were obtained from our breeding colony, which was maintained in a 15L:9-h dark (15L) photoperiod. Onset of darkness was 1800 h Pacific Standard Time for all light-dark cycles. Under light methoxyf lurane vapor anesthesia, testis dimensions were obtained by measuring the length and width of the left testis (Ϯ0.1 mm) with analogue ...

show abstract

Antigonadal Effects of Timed Melatonin Infusion in Pinealectomized Male Djungarian Hamsters (Phodopus sungorus sungorus): Duration is the Critical Parameter*

Cited by 402 publications

References 21 publications

Change in duration of elevated concentrations of melatonin is the major factor in photoperiod response of the tammar, Macropus eugenii

Change in duration of elevated concentrations of melatonin is the major factor in photoperiod response of the tammar, Macropus eugenii

Pineal-dependent and -independent effects of photoperiod on immune function in Siberian hamsters (Phodopus sungorus)

Establishment and persistence of photoperiodic memory in hamsters

Contact Info

Product

Resources

About