In a rat study, a synthetic version of the hormone alpha‑MSH (called (Nle4, D-Phe7)alpha‑MSH) was pumped directly into the brain after a type of brain injury that mimics Parkinson's disease. The treated rats showed better movement, less abnormal turning, and changes in dopamine receptors compared to rats that got just saline. However, the treatment was given by direct brain infusion, which isn’t practical for people, and the work was done in animals, not humans.

Rats were subjected to nigro-striatal hemitransection and then intracerebroventricularly infused with the potent and long-acting alpha-MSH analogue, (Nle4, D-Phe7)alpha-MSH, at two different doses (15 or 30 ng/h/rat), or with saline (0.6 microliter/h/rat), continuously for 14 days starting on day 2 after lesion. (Nle4, D-Phe7)alpha-MSH dose-dependently improved the sensorimotor deficit (postural asymmetry, impaired limb reflexes and coordinated limb use, signs of cortical and pyramidal lesion), reduced turning behaviour induced by apomorphine, and increased spontaneous motility in the open field. 3H-Spiperone binding showed that (Nle4, D-Phe7)alpha-MSH treatment caused a down regulation of the striatal DA receptors in the lesioned side, contrary to the supersensitivity developed by the corresponding receptors of saline treated rats. These results indicate that melanopeptides improve the functional recovery of nigro-striatally hemitransected rats, by an action at CNS level.