NGF and freckles: Also, direct evidence shows that melasma lesions markedly express nerve growth factor receptor (NGFR) and neural endopeptidase (NEP) than nonlesional skin, suggesting that neuroactive molecules, including NGF, may directly affect the microenvironment around melanocytes through a NGFR immunoreactive nerve fiber pathway, and higher levels of NEP have an essential role in the regulation of melanogenesis [69].