Neuropeptide Control of Feeding Behavior in Birds and Its Difference with Mammals
The central mechanisms that mediate neuropeptide K (NPK) associated anorexia are poorly understood in any species, and information in this area of avian biology is totally lacking. Thus, the effects of intracerebroventricular NPK treatment were studied in Cobb-500 chicks (Gallus gallus). In Experiment 1, NPK caused decreased feed intake, but did not affect water intake or whole blood glucose concentration. In Experiment 2, NPK-treated chicks had increased c-Fos immunoreactivity in the parvicellular division of the paraventricular nucleus and arcuate nucleus. The lateral hypothalamus, ventromedial hypothalamus, dorsomedial hypothalamus, periventricular nucleus, magnocellular division of the paraventricular nucleus, and the superchiasmatic nucleus were not affected by NPK treatment. In Experiment 3, the number of feed pecks, exploratory pecks, jumps, escape attempts, and distance moved were decreased, while time spent standing was increased. None of the NPK-treated chicks sat or entered deep rest. In Experiment 4, blockage of corticotrophin releasing factor receptors did not affect NPK-induced anorexia. Thus, we conclude that NPK is a regulator of chick appetite and the effects may be mediated directly in the arcuate nucleus and parvicellular division of the paraventricular nucleus.