• Maria Palomba, Paul Faustin Seke Etet, and Carlo Veronesi.
• Department of Morphology, Surgery and Experimental Medicine, University of Ferrara, Ferrara, Italy. Electronic address: plmmra@unife.it.
• Neurosci. Lett. 2014 Jun 6; 570: 47-52.

AbstractNeurons containing the hypothalamic peptides orexin-A (hypocretin 1) and melanin-concentrating hormone (MCH) have been reported numerous roles in the regulation of the sleep-wake cycle, energy balance and feeding behavior. We investigated the response of these cells to repeated administration of low doses of endotoxin lipopolysaccharide (LPS) in mice. Adult male C57/6J mice where intraperitoneally (i.p.) injected with either LPS or phosphate-buffered saline (PBS) weekly for either 4 or 8 weeks, and afterwards were sacrificed at different time intervals from last injection. A significant drop in orexin-containing neuron number, but not in numbers of MCH or neuronal nuclear antigen (NeuN)-immunoreactive neurons, was observed after 8 weeks of LPS treatment, as compared to PBS treatment. Orexin expression entirely returned to control levels 30 days after the last LPS injection in mice treated for 8 weeks. These data strongly suggest the occurrence of selective alterations of orexinergic system, reversible over time, following repeated and intermittent systemic inflammatory challenge in mice.Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

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