Li A-J, Wang Q, Davis H, Ritter S (2014) Contribution of hindbrain catecholamine neurons to orexin-induced feeding. Neuroscience 2014 Abstracts 834.08. Society for Neuroscience, Washington, DC.
Summary: Both lateral hypothalamic orexinergic neurons and hindbrain catecholaminergic neurons contribute to feeding behavior. In addition, both phenotypes are widely distributed in the brain and their terminal sites are in many cases overlapping. In the hindbrain, both orexin receptor subtypes (OX1R and OX2R) have been found in close proximity to dopamine-β-hydroxylase (DBH)-expressing cell bodies, raising the question of whether orexin stimulates feeding by activating catecholamine neurons. We tested this hypothesis in the present study. First, we implanted rats with fourth ventricular (4V) cannulas and tested feeding in response to 4V injection of orexin (0.5 nmol). Orexin stimulated feeding in rats, and this stimulation was abolished in rats given paraventricular hypothalamic injections of the retrogradely-transported immunotoxin, anti-DBH-saporin, which targets and destroys DBH-expressing neurons. We then examined hindbrain c-Fos expression in normal rats in response to 4V injection of the same orexin dose that stimulated food intake. Using multiple immunofluorescent labels and confocal microscopy we found that most of the orexin-induced c-Fos-immunoreactive (-ir) neurons in the dorsomedial and ventrolateral medulla were DBH-ir and, moreover, that orexin-ir varicosities were situated in close proximity to the Fos-expressing DBH-ir soma. Together these results suggest that orexin stimulates feeding, at least in part, by activating hindbrain catecholamine neurons.
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