Thursday, November 18, 2010

Corticotrophin-releasing factor mediates hypophagia after adrenalectomy, increasing meal-related satiety responses

Ernane Torres Uchoa, Lilian Eslaine Costa Mendes da Silva, Margaret de Castro, Jose Antunes-Rodrigues and Lucila Leico K. Elias

a Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Brazil

b Department of Internal Medicine, School of Medicine of Ribeirao Preto, University of Sao Paulo, Brazil

Adrenalectomy-induced hypophagia is associated with increased satiety-related responses, which involve neuronal activation of the nucleus of the solitary tract (NTS). Besides its effects on the pituitary–adrenal axis, corticotrophin-releasing factor (CRF) has been shown to play an important role in feeding behaviour, as it possesses anorexigenic effects. We evaluated feeding-induced CRF mRNA expression in the paraventricular nucleus (PVN) and the effects of pretreatment with CRF2 receptor antagonist (Antisauvagine-30, AS30) on food intake and activation of NTS neurons in response to feeding in adrenalectomised (ADX) rats. Compared to the sham group, ADX increased CRF mRNA levels in the PVN of fasted animals, which was further augmented by refeeding. AS30 treatment did not affect food intake in the sham and ADX + corticosterone (B) groups; however, it reversed hypophagia in the ADX group. In vehicle-pretreated animals, refeeding increased the number of Fos and Fos/TH-immunoreactive neurons in the NTS in the sham, ADX and ADX + B groups, with the highest number of neurons in the ADX animals. Similarly to its effect on food intake, pretreatment with AS30 in the ADX group also reversed the increased activation of NTS neurons induced by refeeding while having no effect in the sham and ADX + B animals. The present results show that adrenalectomy induces an increase in CRF mRNA expression in the PVN potentiated by feeding and that CRF2 receptor antagonist abolishes the anorexigenic effect and the increased activation of NTS induced by feeding in the ADX animals. These data indicate that increased activity of PVN CRF neurons modulates brainstem satiety-related responses, contributing to hypophagia after adrenalectomy.

Research Highlights

►Primary adrenal insufficiency increases meal-related satiety responses.

►Adrenalectomy-induced hypophagia is associated with increased CRF mRNA expression in the hypothalamic paraventricular nucleus (PVN) and increased NTS neuron activation in the brainstem. ►The increased activity of PVN CRF neurons modulates brainstem satiety-related responses. ►CRF type 2 receptor mediates CRF suppressing effect on food intake after adrenalectomy.

Keywords: Glucocorticoids; Food intake; Corticotrophin-releasing factor; Paraventricular nucleus of the hypothalamus; Nucleus of the solitary tract

Article Outline
Introduction
Experimental procedures
Animals
Intracerebroventricular (icv) surgery
Perfusion, tissue preparation and immunohistochemistry
Microdissection, total RNA isolation and quantitative real-time PCR
Experimental protocols
Experiment 1: effects of ADX and B replacement on CRF mRNA expression in the PVN in the fasting–refeeding regimen
Experiment 2: effects of pretreatment with CRF2 receptor antagonist on food intake in sham, ADX and ADX + B animals
Experiment 3: effects of pretreatment with CRF2 receptor antagonist on NTS neuron activation in sham, ADX and ADX + B animals in the fasting–refeeding regimen
Statistical analysis
Results
Experiment 1: effects of ADX and B replacement on CRF mRNA expression in the PVN in the fasting–refeeding regimen
Experiment 2: effects of pretreatment with CRF2 receptor antagonist on food intake in sham, ADX and ADX + B animals
Experiment 3: effects of pretreatment with CRF2 receptor antagonist on NTS neuron activation in sham, ADX and ADX + B animals in the fasting–refeeding regimen
Discussion
Acknowledgements
References

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Fig. 1.

Relative CRF mRNA expression in the PVN of fasted and refed sham, ADX and ADX + B animals (n = 5–8 rats/group). Data are shown as mean ± SEM. *P < 0.05.

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Fig. 2.

Food intake (g/100 g) after 4 h of refeeding (n = 5–7 rats/group) for sham, ADX and ADX + B animals pretreated with vehicle or d-Phe11,His12-Sauvagine 11–40 (Antisauvagine-30, AS30; 5 μg/5 μL icv). Data are shown as mean ± SEM. *P < 0.05.

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Fig. 3.

Number of Fos-immunoreactive (A) and Fos/TH-immunoreactive (B) neurons in the NTS (n = 4–8 rats/group) of fasted and refed sham, ADX and ADX + B animals pretreated with vehicle or d-Phe11,His12-Sauvagine 11–40 (Antisauvagine-30, AS30; 5 μg/5 μL icv). Data are shown as mean ± SEM. ND: not detectable. *P < 0.05 vs. respective fasted group. #P < 0.05 vs. refed sham/vehicle, refed ADX + B/vehicle and refed ADX/AS30 groups.

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Fig. 4.

Representative photomicrographs (40× magnification) of coronal sections showing Fos/TH immunoreactivity in the NTS of refed sham, ADX and ADX + B animals pretreated with vehicle or d-Phe11,His12-Sauvagine 11–40 (Antisauvagine-30, AS30; 5 μg/5 μL icv). Each inset depicts at 20× magnification the area where the photomicrograph was taken. Scale bar, 100 μm.

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Table 1. Number (means ± SEM) of TH-immunoreactive neurons and percentage of Fos/TH double labelled neurons in the NTS of fasted and refed sham, ADX, and ADX + B animals, pretreated with vehicle or AS30. View table in article

Data are expressed as means ± SEM (n = 4–8 rats/group). NTS, nucleus of the solitary tract; TH, tyrosine hydroxylase.

a P < 0.05 vs. respective fasted group.
b P < 0.05 vs. refed sham/vehicle, refed ADX + B/vehicle and refed ADX/AS30 groups.

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Corresponding Author Contact InformationCorresponding author. Avenida Bandeirantes, 3900, 14049-900 Ribeirao Preto, Sao Paulo, Brazil. Fax: +55 16 3633 0017.


Hormones and Behavior
Volume 58, Issue 5, November 2010, Pages 714-719

From http://www.sciencedirect.com/science