Effect of intracerebroventricular (ICV) injection of adrenomedullin and its interaction with NPY and CCK pathways on food intake regulation in neonatal layer-type chicks.

Adrenomedullin has various physiological roles including appetite regulation. The objective of present study was to determine the effects of ICV injection of adrenomedullin and its interaction with NPY and CCK receptors on food intake regulation. In experiment 1, chickens received ICV injection of saline and adrenomedullin (1, 2, and 3 nmol). In experiment 2, birds injected with saline, B5063 (NPY(1) receptor antagonist, 1.25 µg), adrenomedullin (3 nmol) and co-injection of B5063+adrenomedullin. Experiments 3 to 5 were similar to experiment 2 and only SF22 (NPY(2) receptor antagonist, 1.25 µg), SML0891 (NPY(5) receptor antagonist, 1.25 µg) and CCK(4) (1 nmol) were injected instead of B5063. In experiment 6, ICV injection of saline and CCK(8s) (0.125, 0.25, and 0.5 nmol) were done. In experiment 7, chickens injected with saline, CCK(8s) (0.125 nmol), adrenomedullin (3 nmol) and co-injection of CCK(8s)+adrenomedullin. After ICV injection, birds were returned to their individual cages immediately and cumulative food intake was measured at 30, 60, and 120 min after injection. Adrenomedullin (2 and 3 nmol) decreased food intake compared to control group (P < 0.05). Coinjection of B5063+adrenomedullin amplified hypophagic effect of adrenomedullin (P < 0.05). The ICV injection of the CCK(8s) (0.25 and 0.5 nmol) reduced food intake (P < 0.05). Co-injection of the CCK(8s)+adrenomedullin significantly potentiated adrenomedullin-induced hypophagia (P < 0.05). Administration of the SF22, SML0891 and CCK(4) had no effect on the anorexigenic response evoked by adrenomedullin (P > 0.05). These results suggested that the hypophagic effect of the adrenomedullin is mediated by NPY(1) and CCK(8s) receptors. However, our novel results should form the basis for future experiments.