Anorexigenic effects of central adrenomedullin are associated with hypothalamic changes in juvenile Gallus gallus

Adrenomedullin (AM), a 52 residue neuropeptide, is associated with anorexia in mammals and has a poorly understood central mechanism of action. Thus, this study focused on elucidating AM's central mechanism of action in an alternative vertebrate model, the chick (Gallus gallus). In Experiment 1, chicks centrally injected with AM dose-dependently reduced food but not water intake. In Experiment 2, those chicks that received central AM had increased c-Fos immunoreactivity in the magnocellular division of the paraventricular nucleus (PaMC), ventromedial hypothalamus (VMH) and doromedial hypothalamus (DM). The lateral hypothalamic area, parvocellular division of the paraventricular hypothalamus and the arcuate nucleus were not affected. In Experiment 3, antagonism of corticotrophin releasing factor (CRF) receptors did not affect AM-associated anorexia. In Experiment 4, a comprehensive behavior analysis was conducted and AM-treated chicks pecked less, moved more, jumped more and spent more time in deep rest. In conclusion, exogenous AM induced anorexia is associated with activation of the PaMC, VMH and DM of the hypothalamus, is not CRF dependent, and affects behaviors unrelated to food intake in chicks.