Seasonal and state-dependent changes in brain TRH receptors in hibernating ground squirrels

Stanton, Toni L.; Caine, S. Barak; Winokur, Andrew

doi:10.1016/0361-9230(92)90208-f

Cited by 17 publications

(7 citation statements)

References 60 publications

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“…It can be hypothesized that TRH produces a direct neurohormonal effect on vasopressinergic cells in the PVN and SON. This hypothesis agrees with evidence on the existence of TRH-receptors in nerve cells of the hypothalamus [8,13,14]. TRH inhibits protein synthesis in vasopressinergic cells, which is manifested in a rapid decrease in the size of their nucleoli and indirectly supported by the data on a drop of blood vasopressin after TRH injection [1,9].…”

Section: R Es U Ltssupporting

confidence: 83%

Effect of thyroliberin on nonapeptidergic cells in cultured rat hypothalamic slices

Глазова

Krasnovskaya

1999

Bull Exp Biol Med

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The direct effect of thyroliberin on nonapeptidergic cells of the supraoptic and paraventricular nuclei was studied on cultured rat hypothalamic slices. Incorporation of labeled thyroliberin into vasopressinergic and oxytocinergic cells and a decrease in functional activity of these cells were observed in both hypothalamic nuclei. Key Words: thyroliberin; vasopressin; oxytocin; hypothalamus; paraventricular nucleus; supraoptic nucleusMost peptide hypothalamic hormones act as neurohormones affecting the target cells via blood and liquor and as neurotransmitters, i.e. affect other nerve cells (including those producing neurohormones) via the corresponding synapses [7]. There is evidence on the presence of corticoliberinergic synapses of cells of the paraventricular hypothalamic nucleus (PVN) that produce thyroliberin (TRH) [12]. Somatostatin-and somatoliberin-producing cells of the arcuate nucleus also interact via synaptic connections [11 ].The interaction between the cells producing releasing-hormones, in particular between TRH-cells and nonapeptidergic cells in the hypothalamic PVN and supraoptic nucleus (SON) remains unclear. The existence of such connections is confirmed by the thyreostimulating effect of vasopressin and oxytocin [2][3][4] and by the effect of TRH on the functional state of PVN and SON cells in vivo [1,9]. However, the data obtained in vivo provide little information on the mechanism of TRH action on nonapeptidergic cells. Our aim was to carry out a morphofunctional study of vasopressin-and oxytocinergic cells in isolated hypothalamic slices exposed to TRH. MATERIALS AND METHODSThe study was carried out on mature male Wistar rats weighing 120-140 g kept under standard vivarium Laboratory-of Neuroendocrinology, I. M. Sechenov Institute of Evolution, Physiology, and Biochemistry, Russian Academy of Sciences, St. Petersbur 9 conditions. After decapitation, the brain was rapidly removed and 400-p slices contaimng SON and/or PVN were prepared from the hypothalamic area. The slices were preincubated in Earle's medium aerated with carbogen (95% 02+5% CO2) at 37~ Preincubation was performed in 3 portions of the growth medium (30 min in each portion).In the first experimental series we studied incorporation of 3H-TRH into neurosecretory cells of PVN and SON. After preincubation, the hypothalamic slices were transferred to the growth medium with 3H-TRH (1.75• 1.85x106 Bq/mol, NEN Product) and incubated for 15 and 30 min (the medium was changed every 15 min).The slices were fixed in picric acid and formalin (3:5) and processed by standard histological methods. Serial sections (6 p) were used in immunohistochemical PAP-reaction pertormed with nonlabeled antibodies to oxytocin. The sections were covered with an M-type photoemulsion (KhimFotoProekt, Moscow), exposed for 6 weeks, and developed in 2,4-diaminophenol dihydrochloride. Binding of 3H-TRH in PVN and SON cells was accesses by the number of silver grains concentrated above one cell (30 vasopressin-and 30 oxytocinergic cells for each rat). The number ...

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Section: R Es U Ltssupporting

confidence: 83%

Effect of thyroliberin on nonapeptidergic cells in cultured rat hypothalamic slices

Глазова

Krasnovskaya

1999

Bull Exp Biol Med

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“…An example is the ADS activity in ground squirrels being highly seasonally affected and parallels other regulatory factors such as monoamine oxidase (MAO) activity (52,53). However, it has been proposed that general thermoregulation of euthermic hibernators does not differ from that of non-hibernators and that a hibernating mammal, during euthermia, functions physiologically and behaviorally in the same manner as any non-hibernating mammal (54).…”

Section: Heterotherms and Ectothermsmentioning

confidence: 99%

Cold defence responses the role of oxidative stress

Blagojević

Grubor-Lajsic²,

Spasić³

2011

Front Biosci

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Low temperatures provoke increased production of heat accompanied by increased respiration, oxygen consumption and the production of partially reduced oxygen species called ROS. ROS induce different forms of cellular oxidative damage, disturb the redox state and can change the activity of several metabolic enzymes. Organisms have developed a functionally connected set of anti-oxidant enzymes and low molecular mass compounds (together termed the ADS) that metabolise primary ROS. If ROS production within cells overwhelms the ADS, oxidative damage arises and oxidative stress can occur. Short-term cold exposure in endotherms leads to oxidative stress. As cold exposure persists organisms develop adaptive changes toward reducing ROS production and increasing the ADS. In contrast, heterotherms and ectotherms as a normal part of their over-wintering strategy slow down metabolism, oxygen consumption and subsequently cause ROS production. Increased baseline activity of key anti-oxidant enzymes as well as 'secondary' enzymatic defence and/or glutathione levels in preparation for a putative oxidative stressful situation arising from tissue re-oxygenation seems to be the preferred evolutionary adaptation of such animals exposed to low environmental temperatures.

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“…It has been shown that both AVP injection in the lateral septum (Hermes et al, ) and intracerebroventricular injection of TRH (Tamura et al, ) interrupt torpor and induce arousal. In addition, TRH receptor quantification in ground squirrel shows seasonal variations (Stanton et al, ). TRH receptor density decreases in torpor compared with euthermia in the PVN and in the medial preoptic area of the POA, both thermoregulatory regions (Stanton et al, ).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, TRH receptor quantification in ground squirrel shows seasonal variations (Stanton et al, ). TRH receptor density decreases in torpor compared with euthermia in the PVN and in the medial preoptic area of the POA, both thermoregulatory regions (Stanton et al, ). As TRH is linked to metabolic state, we can speculate that a metabolic clue may trigger thermogenesis, however the signaling mechanisms initiating rewarming are still unknown (Drew et al, ).…”

Section: Discussionmentioning

confidence: 99%

Seasonal decrease in thermogenesis and increase in vasoconstriction explain seasonal response to N⁶‐cyclohexyladenosine‐induced hibernation in the Arctic ground squirrel (Urocitellus parryii)

Frare

Jenkins

McClure

et al. 2019

Journal of Neurochemistry

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Hibernation is a seasonal phenomenon characterized by a drop in metabolic rate and body temperature. Adenosine A1 receptor agonists promote hibernation in different mammalian species, and the understanding of the mechanism inducing hibernation will inform clinical strategies to manipulate metabolic demand that are fundamental to conditions such as obesity, metabolic syndrome, and therapeutic hypothermia. Adenosine A1 receptor agonist‐induced hibernation in Arctic ground squirrels is regulated by an endogenous circannual (seasonal) rhythm. This study aims to identify the neuronal mechanism underlying the seasonal difference in response to the adenosine A1 receptor agonist. Arctic ground squirrels were implanted with body temperature transmitters and housed at constant ambient temperature (2°C) and light cycle (4L:20D). We administered CHA (N6‐cyclohexyladenosine), an adenosine A1 receptor agonist in euthermic‐summer phenotype and euthermic‐winter phenotype and used cFos and phenotypic immunoreactivity to identify cell groups affected by season and treatment. We observed lower core and subcutaneous temperature in winter animals and CHA produced a hibernation‐like response in winter, but not in summer. cFos‐ir was greater in the median preoptic nucleus and the raphe pallidus in summer after CHA. CHA administration also resulted in enhanced cFos‐ir in the nucleus tractus solitarius and decreased cFos‐ir in the tuberomammillary nucleus in both seasons. In winter, cFos‐ir was greater in the supraoptic nucleus and lower in the raphe pallidus than in summer. The seasonal decrease in the thermogenic response to CHA and the seasonal increase in vasoconstriction, assessed by subcutaneous temperature, reflect the endogenous seasonal modulation of the thermoregulatory systems necessary for CHA‐induced hibernation. Cover Image for this issue: doi: .

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Seasonal and state-dependent changes in brain TRH receptors in hibernating ground squirrels

Cited by 17 publications

References 60 publications

Effect of thyroliberin on nonapeptidergic cells in cultured rat hypothalamic slices

Effect of thyroliberin on nonapeptidergic cells in cultured rat hypothalamic slices

Cold defence responses the role of oxidative stress

Seasonal decrease in thermogenesis and increase in vasoconstriction explain seasonal response to N⁶‐cyclohexyladenosine‐induced hibernation in the Arctic ground squirrel (Urocitellus parryii)

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Seasonal and state-dependent changes in brain TRH receptors in hibernating ground squirrels

Cited by 17 publications

References 60 publications

Effect of thyroliberin on nonapeptidergic cells in cultured rat hypothalamic slices

Effect of thyroliberin on nonapeptidergic cells in cultured rat hypothalamic slices

Cold defence responses the role of oxidative stress

Seasonal decrease in thermogenesis and increase in vasoconstriction explain seasonal response to N6‐cyclohexyladenosine‐induced hibernation in the Arctic ground squirrel (Urocitellus parryii)

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Seasonal decrease in thermogenesis and increase in vasoconstriction explain seasonal response to N⁶‐cyclohexyladenosine‐induced hibernation in the Arctic ground squirrel (Urocitellus parryii)