The influence of melanocortin peptides on neuronal function was first suggested from observation of the effects of pituitary removal coupled with melanocortin hormone replacement therapy. Melanocortin hormones have been shown to enhance performance in behavioral tests requiring learning and memory, 1 regeneration ability following axon damage, 2

impulse transmission at the neuromuscular junction,3 brain protein synthesis,4 and fetal brain development. 5 The spectrum of melanocortin actions suggests that such peptides may possess neurotrophic activity and be involved in interactions between neurons and their postsynaptic targets.