Nitric oxide and fever: immune-to-brain signaling vs. thermogenesis in chicks

Nitric oxide (NO) plays a role in thermogenesis but does not mediate immune-to-brain febrigenic signaling in rats. There are suggestions of a different situation in birds, but the underlying evidence is not compelling. The present study was designed to clarify this matter in 5-day-old chicks challen...

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Published in:American journal of physiology. Regulatory, integrative and comparative physiology integrative and comparative physiology, 2016-05, Vol.310 (10), p.R896-R905
Main Authors: Dantonio, Valter, Batalhão, Marcelo E, Fernandes, Marcia H M R, Komegae, Evilin N, Buqui, Gabriela A, Lopes, Norberto P, Gargaglioni, Luciane H, Carnio, Évelin C, Steiner, Alexandre A, Bícego, Kênia C
Format: Article
Language:English
Subjects:
Animals
Behavior, Animal
Body Temperature Regulation - physiology
Brain - physiology
Chickens - physiology
Dinoprostone - metabolism
Fever
Fever - chemically induced
Lipopolysaccharides - toxicity
NG-Nitroarginine Methyl Ester - pharmacology
Nitrates - metabolism
Nitric oxide
Nitric Oxide - metabolism
Nitrites - metabolism
Signal transduction
Signal Transduction - physiology
Thermogenesis
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Summary:Nitric oxide (NO) plays a role in thermogenesis but does not mediate immune-to-brain febrigenic signaling in rats. There are suggestions of a different situation in birds, but the underlying evidence is not compelling. The present study was designed to clarify this matter in 5-day-old chicks challenged with a low or high dose of bacterial LPS. The lower LPS dose (2 μg/kg im) induced fever at 3-5 h postinjection, whereas 100 μg/kg im decreased core body temperature (Tc) (at 1 h) followed by fever (at 4 or 5 h). Plasma nitrate levels increased 4 h after LPS injection, but they were not correlated with the magnitude of fever. The NO synthase inhibitor (N(G)-nitro-l-arginine methyl ester, l-NAME; 50 mg/kg im) attenuated the fever induced by either dose of LPS and enhanced the magnitude of the Tc reduction induced by the high dose in chicks at 31-32°C. These effects were associated with suppression of metabolic rate, at least in the case of the high LPS dose. Conversely, the effects of l-NAME on Tc disappeared in chicks maintained at 35-36°C, suggesting that febrigenic signaling was essentially unaffected. Accordingly, the LPS-induced rise in the brain level of PGE2 was not affected by l-NAME. Moreover, l-NAME augmented LPS-induced huddling, which is indicative of compensatory mechanisms to run fever in the face of attenuated thermogenesis. Therefore, as in rats, systemic inhibition of NO synthesis attenuates LPS-induced fever in chicks by affecting thermoeffector activity and not by interfering with immune-to-brain signaling. This may constitute a conserved effect of NO in endotherms.
ISSN:0363-6119
1522-1490
DOI:10.1152/ajpregu.00453.2015