Effective delivery of NGF into the CNS parenchyma is still challenging due mainly to its limited ability to cross the blood–brain barrier, and intolerable side effects (pain, aberrant sympathetic, sensory neurite sprouting, and weight loss) if administered into the brain ventricular system Intranasal administration of NGF rescued recognition memory deficits in an anti-NGF transgenic mouse model which shows typical features of AD [10–12]. This evidence concerns the gene NGF and Alzheimer disease.