Melanocortinergic activation by melanotan II inhibits feeding and increases uncoupling protein 1 messenger ribonucleic acid in the developing rat.

The hypothalamic neurocircuitry that regulates energy homeostasis in adult rats is not fully developed until the third postnatal week. In particular, fibers from the hypothalamic arcuate nucleus, including both neuropeptide Y (NPY) and alpha-MSH fibers, do not begin to innervate downstream hypothalamic targets until the second postnatal week. However, alpha-MSH fibers from the brainstem and melanocortin receptors are present in the hypothalamus at birth.