Nogo-66(1-40) is a synthetic peptide representing residues 1-40 of the Nogo-66 inhibitory domain from the Nogo-A protein. It binds to the Nogo-66 receptor (NgR1) on neurons, triggering intracellular signaling that inhibits axonal growth and neurite outgrowth. Widely used in neuroscience research to investigate myelin-associated growth inhibition and neural regeneration mechanisms, particularly in models of spinal cord injury. Serves as a tool to study regenerative failure in the central nervous system and to screen for antagonists or blockers of the Nogo-66/NgR1 interaction, which can promote neurite outgrowth and potential therapeutic recovery from trauma or neurodegenerative diseases.