Central calcitonin exerts anorectic effects via the hypothalamus in chicks

Calcitonin (CT) causes satiety in mammals, but the mechanisms that mediate this effect are poorly understood. Additionally, there are no reports on CT-induced satiety within the avian class. Therefore, the purpose of this study was to elucidate some of the central mechanisms regulating CT-induced satiety in a non-mammalian vertebrate, the chick. Broiler-type chicks, at 4 days of age, responded to central CT (0.3, 1.0 and 3.0 nmol) with both reduced food and water intake. The effect on water intake was secondary to that of food. An increased number of c-Fos immunoreactive cells were found in hypothalamic nuclei associated with satiety including the arcuate nucleus, dorsomedial nucleus and ventromedial hypothalamus after central CT injection. Increased jumps, distance traveled and time spent perching on food containers were also observed, and these behaviors are likely not competitive with ingestion. Also, central CT injection was associated with reduced food pecks, but increased pecking efficiency. Blockage of corticotrophin releasing factor receptors did not prevent central CT-induced satiety. Central CT appears to be a regulator of satiety in chicks and this effect is likely mediated via interactions within the hypothalamus.