Effect of asymmetrical reductions of photoperiod on pineal melatonin, locomotor activity and gonadal condition of male Syrian hamsters

Hastings, Michael H.; Walker, Alonzo P.; Herbert, J.

doi:10.1677/joe.0.1140221

Cited by 69 publications

(48 citation statements)

References 18 publications

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“…The observation that melatonin secretion in European hamsters is attenuated at a T a of 30°C supports this conjecture (45). The ␣-value is a reliable indicator of the duration of the nocturnal melatonin signal in Syrian hamsters at 22°C (11,20); whether this relation holds at lower (5°C) or higher (28-32°C) T a values is not known and therefore requires qualification of these conclusions. In Syrian hamsters held in LDs and treated with supplementary midafternoon melatonin injections, the gonadal response was diminished at T a values of 30-32°C compared with responses at 22°C (26,35).…”

Section: Discussionmentioning

confidence: 90%

Temperature dependence of gonadal regression in Syrian hamsters exposed to short day lengths

Larkin¹,

Jones

Zucker

2002

American Journal of Physiology-Regulatory, Integrative and Comp

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We sought to determine whether ambient temperature (Ta) affects gonadal function by altering the rate at which circadian rhythms entrain to short day lengths. Syrian hamsters were housed in cages where they received 14 h of light per day (“long days,” 14L) at 22°C. Hamsters were then transferred to cages to receive 10 h of light per day (“short days,” 10L) and kept at 5, 22, or 28°C or were maintained in 14L at 22°C. Body mass and estimated testis volume as well as duration of nocturnal locomotor activity (α), previously established as a reliable indicator of the duration of nocturnal melatonin secretion, were determined over the course of 24 wk. Testicular regression in short days was accelerated by 4 wk at 5°C and delayed by 3 wk at 28°C relative to 22°C. The interval between α-expansion and initiation of testicular regression was markedly affected by Ta with delays of 0, 3, and 6 wk at 5, 22, and 28°C, respectively. All hamsters held at 5 and 22°C underwent testicular regression, but 25% of those maintained at 28°C failed to do so. We suggest that Ta modulates testicular regression primarily by affecting responsiveness of neuroendocrine target tissues to long melatonin signals.

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Section: Discussionmentioning

confidence: 90%

Temperature dependence of gonadal regression in Syrian hamsters exposed to short day lengths

Larkin¹,

Jones

Zucker

2002

American Journal of Physiology-Regulatory, Integrative and Comp

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“…Similarly, the transfer of Syrian hamsters from LD to SD leads to a decrease in gene expression only after 14 days. In Syrian hamsters, after a transfer from LD to SD, the duration of melatonin synthesis slowly increases; this phenomenon is known as decompression and can take up to 8 weeks to complete (20). However, after only 2 weeks, the duration of melatonin synthesis under SD is already double that of LD (20), and this could allow the melatonin signal to inhibit the expression of the Per1 and ICER peaks.…”

Section: Discussionmentioning

confidence: 99%

Decoding photoperiodic time through Per1 and ICER gene amplitude

Messager¹,

Ross²,

Barrett³

et al. 1999

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

177

176

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The mammalian Per1 gene is expressed in the suprachiasmatic nucleus of the hypothalamus, where it is thought to play a critical role in the generation of circadian rhythms. Per1 mRNA also is expressed in other tissues. Its expression in the pars tuberalis (PT) of the pituitary is noteworthy because, like the suprachiasmatic nucleus, it is a known site of action of melatonin. The duration of the nocturnal melatonin signal encodes photoperiodic time, and many species use this to coordinate physiological adaptations with the yearly climatic cycle. This study reveals how the duration of photoperiodic time, conveyed through melatonin, is decoded as amplitude of Per1 and ICER (inducible cAMP early repressor) gene expression in the PT. Syrian hamsters display a robust and transient peak of Per1 and ICER gene expression 3 h after lights-on (Zeitgeber time 3) in the PT, under both long (16 h light͞8 h dark) and short (8 h light͞16 h dark) photoperiods. However, the amplitude of these peaks is greatly attenuated under a short photoperiod. The data show how amplitude of these genes may be important to the long-term measurement of photoperiodic time intervals.

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“…In general. hamsters 01 16L : 8 D in our colony become active 30 to 60 min before the onset 01 the dark phase (38). Animals killed 2 h after the onset of dark were cc isidered to be between CT 14 and CT 15.…”

Section: Discussionmentioning

confidence: 99%

The Role of N‐Methyl‐D‐Aspartate‐Type Glutamatergic Neurotransmission in the Photic Induction of Immediate‐Early Gene Expression in the Suprachiasmatic Nuclei of the Syrian Hamster

Ebling

Maywood

Staley

et al. 1991

J Neuroendocrinology

Self Cite

126

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This study investigated the role of N-methyl-D-aspartate (NMDA)-type glutamatergic neurotransmission in mediating the photic indu1;tion of immediate-early gene expression in the suprachiasmatic nucleus (SCN) of the Syrian hamster. Activation of c-fos, c-ju,: and egr-7 was assessed by immunocytochemical detection of their protein products. To characterize the circadian basis to the i.iductive effects of light, hamsters were allowed to free-run in constant dim red light and received a 1 h light pulse at different circadian phases relative to activity onset (defined as CT 12). In control animals which did not receive light pulses, c-fos and egr-I expression was absent or restricted to a small area of the dorsolateral region of the SCN, and expression of c-jun could not be detected in the SCN. In hamsters killed after presentation of a light pulse at either CT 14 or CT 20, there was a marked increase in c-fos and egr-7 immunoreactivities throughout the ventrolateral division of the SCN. In contrast, light pulses given at CT 4 or CT 8 failed to activate immediate-early gene expression. Light pulses did not induce c-jun immunoreactivity at any circadian phase tested. Staining for c-fos was maximal 1 h after the start of the light pulse and had started to decline by 2 h. At this later time, c-jun expression was still undetectable. To compare the distribution of retinal afferents with that of c-fos induction, hamsters held on a light schedule of 16 h light : 8 h dark received an intraocular injection of cholera toxin-horseradish peroxidase conjugate 3 days before exposure to a 1 h light pulse given 2 h after lights off. Comparison of adjacent sections processed for c-fos immmoreactivity or for cholera toxin-horseradish peroxidase revealed that light-induced c-fos expression was precisely restricted to rviinal terminal fields in the SCN. Light pulses also induced c-fos expression in the retinoreceptive ventral lateral geniculate nucl1:us and intergeniculate leaflet but not in the retinal fields of the dorsal lateral geniculate nucleus, indicating that the expression Of C -W S in response to light is spatially specific.The aim of the subsequent experiments was to investigate the role of NMDA-type glutamatergic neurotransmission in mediating the cffects of light on c-fos expression in the SCN. To determine whether NMDA had the potential to activate c-fos expression in the SCN, hamsters were infused with 2.5 nmol NMDA or vehicle via an intracerebroventricular (icv) cannula positioned adjacent to the nuclei. In contrast to the effects of light, icv NMDA activated c-fos expression at both CT 8 and CT 14. The distribution of imm!rnoreactivity was more widespread than that observed after light, extending throughout the SCN and adjacent hypothalamus. TO test whether NMDA receptors had a physiological role in the photic response, hamsters were treated systemically with the non-competitive NMDA antagonist MK801 (dose range 0.6 to 6.0 mg/kg body wt, ip) or vehicle prior to exposure to a 1 h light pulse given at CT 14 or CT ...

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Effect of asymmetrical reductions of photoperiod on pineal melatonin, locomotor activity and gonadal condition of male Syrian hamsters

Cited by 69 publications

References 18 publications

Temperature dependence of gonadal regression in Syrian hamsters exposed to short day lengths

Temperature dependence of gonadal regression in Syrian hamsters exposed to short day lengths

Decoding photoperiodic time through Per1 and ICER gene amplitude

The Role of N‐Methyl‐D‐Aspartate‐Type Glutamatergic Neurotransmission in the Photic Induction of Immediate‐Early Gene Expression in the Suprachiasmatic Nuclei of the Syrian Hamster

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