Photoperiodic Control of Reproduction in Olfactory-Bulbectomized Rats

Nelson, Randy J.; Zucker, Irving H.

doi:10.1159/000123171

Cited by 101 publications

(51 citation statements)

References 33 publications

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“…Although Sprague Dawley rats are not known to respond to photoperiods with altered physiology or behaviour, the potential for signalling of TSH secreted from the pars tuberalis is present in this rat strain with the presence of a functional TSH receptor located in the ventricular ependymal layer. However, the applicability of the present findings may be more generic rather than merely applicable to mammals that are normally associated with seasons, as most laboratory strains of rats have the potential to respond to photoperiods with physiological changes following olfactory bulbectomy (Nelson & Zucker 1981) or after manipulation of testosteronenegative feedback (Wallen et al 1987). Moreover, the F344 rat strain does show physiological responses to photoperiods in terms of food intake and body weight (Ross et al 2011) and increases in Dio2 expression in the ependymal layer following i.c.v.…”

Section: Discussionmentioning

confidence: 98%

Dual signal transduction pathways activated by TSH receptors in rat primary tanycyte cultures

Bolborea¹,

Helfer²,

Ebling³

et al. 2015

Journal of Molecular Endocrinology

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Tanycytes play multiple roles in hypothalamic functions, including sensing peripheral nutrients and metabolic hormones, regulating neurosecretion and mediating seasonal cycles of reproduction and metabolic physiology. This last function reflects the expression of TSH receptors in tanycytes, which detect photoperiod-regulated changes in TSH secretion from the neighbouring pars tuberalis. The present overall aim was to determine the signal transduction pathway by which TSH signals in tanycytes. Expression of the TSH receptor in tanycytes of 10-day-old Sprague Dawley rats was observed by in situ hybridisation. Primary ependymal cell cultures prepared from 10-day-old rats were found by immunohistochemistry to express vimentin but not GFAP and by PCR to express mRNA for Dio2, Gpr50, Darpp-32 and Tsh receptors that are characteristic of tanycytes. Treatment of primary tanycyte/ependymal cultures with TSH (100 IU/l) increased cAMP as assessed by ELISA and induced a cAMP-independent increase in the phosphorylation of ERK1/2 as assessed by western blot analysis. Furthermore, TSH (100 IU/l) stimulated a 2.17-fold increase in Dio2 mRNA expression. We conclude that TSH signal transduction in cultured tanycytes signals via Ga s to increase cAMP and via an alternative G protein to increase phosphorylation of ERK1/2.

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Section: Discussionmentioning

confidence: 98%

Dual signal transduction pathways activated by TSH receptors in rat primary tanycyte cultures

Bolborea¹,

Helfer²,

Ebling³

et al. 2015

Journal of Molecular Endocrinology

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“…Thus, photoperiodic changes in the nocturnal duration of melatonin production and locomotor activity-compressed during long days and decompressed during short days-are likely to reflect changes in the SCN itself, suggesting that the nucleus is involved in processing photoperiodic information from the environment. Although the rat is only marginally photoperiodic (22,23), it may be sensitized to the effects of photoperiod by neonatal treatment with testosterone propionate (24), olfactory bulbectomy (25), or undernutrition (26).…”

Section: Discussionmentioning

confidence: 99%

The rat suprachiasmatic nucleus is a clock for all seasons.

Sumová

Travnickova

Peters

et al. 1995

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

163

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Seasonal changes of daylength (photoperiod) affect the expression of hormonal and behavioral circadian rhythms in a variety of organisms. In mammals, such effects might reflect photoperiodic changes in the circadian pacemaking system [located in the suprachiasmatic nucleus (SCN) of the hypothalamus] that governs these rhythms, but to date no functionally relevant, intrinsic property of the SCN has been shown to be photoperiod dependent. We have analyzed the temporal regulation of light-induced c-fos gene expression in the SCN of rats maintained in long or short photoperiods. Both in situ hybridization and immunohistochemical assays show that the endogenous circadian rhythm of light responsiveness in the SCN is altered by photoperiod, with the duration of the photosensitive subjective night under the short photoperiod 5-6 h longer than under the long photoperiod. Our results provide evidence that a functional property of the SCN is altered by photoperiod and suggest that the nucleus is involved in photoperiodic time measurement. Over the course of the year, most mammals respond to seasonal changes of daylength (photoperiod) with altered physiology and behavior. Photoperiodic information from the environment is conveyed to the organism by a circadian rhythm of melatonin production in the pineal gland (1-4). In the rat, rhythmic melatonin production is driven by a circadian rhythm of the activity of pineal N-acetyltransferase (NAT), which synthesizes the melatonin precursor N-acetylserotonin (5, 6). The NAT rhythm is controlled by a light-entrainable circadian pacemaking system in the suprachiasmatic nucleus (SCN) of the hypothalamus; SCN lesions abolish this rhythm (7). Norepinephrine released at night from sympathetic nerve endings in the pineal gland stimulates adrenergic receptors and the cAMP pathway; the resulting induction and activation of pineal NAT activity leads to high nighttime melatonin levels (8). In the rat, the NAT rhythm is entrained to the 24-h light-dark (LD) cycle primarily by light onset at dawn (9). With longer daylengths, light at an earlier dawn advances the phase of the morning NAT decline, while light at a later dusk delays the phase of the evening NAT rise (3, 10). The resulting alteration in the duration of the nocturnal melatonin signal, compressed during long summer days and decompressed during short winter days, appears to serve as an endogenous photoperiodic message (2,3,11).When rats and hamsters are transferred from a long to a short photoperiod, the decompression of the melatonin signal occurs gradually (12-14). Since high NAT activity can be induced independent of the photoperiod by administration of a ,B-adrenergic agonist (15), it seems likely that the neural substrate for this gradual decompression lies upstream of the pineal gland, perhaps in the SCN. Importantly, another circadian rhythm governed by the SCN is photoperiodic. The duration of nocturnal locomotor activity (a) in hamsters is also compressed during long days and decompressed during short days (16, 17)...

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“…In contrast to the outbred non-tropical rodents described above, many laboratory mouse (Mus musculus) and rat (Rattus norvegicus) strains are reproductively non-photoperiodic, although they possess the neuroendocrine mechanisms sufficient for perceiving changes in day length and for transducing ambient photoperiod into a neuroendocrine melatonin signal (Illnerova and Vanecek, 1980;Nelson et al, 1994;Nelson and Zucker, 1981;Wallen and Turek, 1981). Reproductively non-photoperiodic rats and mice thus may provide useful models to investigate mechanisms by which day length influences the immune system in a manner uncomplicated by photoperiodic influences on the reproductive system.…”

Section: Introductionmentioning

confidence: 99%

Winter day lengths enhance T lymphocyte phenotypes, inhibit cytokine responses, and attenuate behavioral symptoms of infection in laboratory rats

Prendergast¹,

Kampf-Lassin²,

Yee³

et al. 2007

Brain, Behavior, and Immunity

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Annual variations in day length (photoperiod) trigger changes in the immune and reproductive system of seasonally-breeding animals. The purpose of this study was to determine whether photoperiodic changes in immunity depend on concurrent photoperiodic responses in the reproductive system, or whether immunological responses to photoperiod occur independent of reproductive responses. Here we report photoperiodic changes in enumerative, functional, and behavioral aspects of the immune system, and in immunomodulatory glucocorticoid secretion, in reproductively non-photoperiodic Wistar rats. T-cell numbers (CD3+, CD8+, CD8+CD25+, CD4+CD25+) were higher in the blood of rats housed in short as opposed to long day lengths for 10 weeks. Following a simulated bacterial infection (E. coli LPS; 125 μg/kg) the severity of several acute-phase sickness behaviors (anorexia, cachexia, neophobia, and social withdrawal) were attenuated in short days. LPS-stimulated IL-1β and IL-6 production were comparable between photoperiods, but plasma TNFα was higher in longday relative to short-day rats. In addition, corticosterone concentrations were higher in short-day relative to long-day rats. The data are consistent with the hypothesis that photoperiodic regulation of the immune system can occur entirely independently of photoperiodic regulation of the reproductive system. In the absence of concurrent reproductive responses, short days increase the numbers of leukocytes capable of immunosurveillance and inhibition of inflammatory responses, increase proinflammatory cytokine production, increase immunomodulatory glucocorticoid secretion, and ultimately attenuate behavioral responses to infection. Seasonal changes in the host immune system, endocrine system, and behavior may contribute to the seasonal variability in disease outcomes, even in reproductively non-photoperiodic mammals.

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Photoperiodic Control of Reproduction in Olfactory-Bulbectomized Rats

Cited by 101 publications

References 33 publications

Dual signal transduction pathways activated by TSH receptors in rat primary tanycyte cultures

Dual signal transduction pathways activated by TSH receptors in rat primary tanycyte cultures

The rat suprachiasmatic nucleus is a clock for all seasons.

Winter day lengths enhance T lymphocyte phenotypes, inhibit cytokine responses, and attenuate behavioral symptoms of infection in laboratory rats

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