Effect of central and peripheral injection of prostaglandin E2 and F2α on feeding and the crop-emptying rate in chicks.

Prostaglandins (PGs) have been shown to cause several physiological changes in mammals including anorexia, awakening and sleeping, change in digestive function, and activation of the hypothalamus-pituitary-adrenal gland (HPA) axis. However, there is a paucity of information about the effect of PGs on physiological parameters in birds. The purpose of the present study was to clarify whether intracerebroventricular (ICV) and intraperitoneal (IP) injections of prostaglandin E2 (PGE2) and prostaglandin F2α (PGF2α) affect feeding, voluntary movement, crop-emptying rate, and corticosterone release in chicks (Gallus gallus). ICV injection of either PGE2 or PGF2α (2 and 4μg) significantly decreased food intake in chicks. The anorexigenic effect was also observed after IP injection of the PGs. Voluntary movement was significantly suppressed by ICV injection of PGE2 or PGF2α, although the time-course change was different between the two. In contrast, IP injection of the PGs had no or less effect on voluntary movement. Both ICV and IP injection of PGE2 significantly retarded the crop-emptying rate, whereas PGF2α significantly lowered the crop-emptying rate only after IP injection. The plasma corticosterone concentration significantly increased after ICV and IP injection of PGE2, whereas PGF2α had no effect. These results suggest that central and peripheral PGs are involved in the regulation of appetite, voluntary movement, food passage in the digestive tract, and activation of the HPA axis in chicks, although the effects depend on the site of action and type of PGs.