Stress inhibits feeding behavior in all vertebrates. Data from mammals suggest an important role for hypothalamic neuropeptides, in particular the melanocortins and corticotropin-releasing hormone (CRH)-like peptides, in mediating stress-induced inhibition of feeding. The effects of CRH on food intake are evolutionarily ancient, as this peptide inhibits feeding in fishes, birds, and mammals. The effects of melanocortins on food intake have not been as extensively studied, but available evidence suggests that the anorexic role of neuronal melanocortins has been conserved. Although there is evidence that CRH and the melanocortins influence hypothalamic circuitry controlling food intake, these peptides may have a more primitive role in modulating visuomotor pathways involved in the recognition and acquisition of food. Stress rapidly reduces visually guided prey-catching behavior in toads, an effect that can be mimicked by administration of CRH, while corticosterone and isoproterenol are without effect. Melanocortins also reduce prey-oriented turning movements and, in addition, facilitate the acquisition of habituation to a moving prey item. The effects of these neuropeptides are rapid, occurring within 30 min after administration. Thus, changes in neuroendocrine status during stress may dramatically influence the efficacy with which visual stimuli release feeding behavior. By modulating visuomotor processing these neuropeptides may help animals make appropriate behavioral decisions during stress.
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Vol. 42 • No. 3