Central α-melanocyte stimulating hormone attenuates behavioral effects of neuropeptide Y in chicks

This experiment was conducted to determine the effects of central α-melanocyte stimulating hormone (α-MSH) and its interaction with neuropeptide Y (NPY) on ingestive and non-ingestive behaviors in chicks. Chicks received intracerebroventricular injections of either 0, 0.12 nM α-MSH, 0.06 nM NPY, or 0.12 nM α-MSH + 0.06 nM NPY. Immediately following injection, chicks were placed in an observation arena and the number of steps, jumps, feed pecks, drinks, exploratory pecks, escape attempts, the total distance traveled, and the amount of time spent standing, sitting, sleeping, and preening were monitored for 60 min. Chicks treated with NPY consumed 69% more feed than controls whereas α-MSH-treated chicks consumed 71% less. Feed intake of the NPY + α-MSH groups was similar to α-MSH-treated chicks at 66% less than aCSF-treated chicks. Differences in pecking were found and followed a similar pattern as feed intake. All treatments increased the amount of time chicks were in a sitting posture, and the α-MSH + NPY group spent more time sitting than α-MSH and NPY alone. The sitting response after α-MSH + NPY treatment was similar to the α-MSH group but not the NPY group. Other behaviors were not affected by treatment. Thus, we conclude that α-MSH, at a concentration that causes a similar magnitude decrease in feed intake as NPY increases feed intake, is a more potent appetite-related signal than NPY. α-MSH causes behavioral effects that may secondarily affect feed intake at a low magnitude and may modulate the behavioral effects of NPY in chicks, contributing to the overall effect on feed intake.