PTN and Alzheimer disease: PTN is overexpressed in different brain areas in situations with inflammatory component, as in brain damage due to ischemia, in neuropathic pain, after administration of different drugs of abuse such as amphetamine, alcohol and opioids, even in neurodegenerative processes, in senile plaques in the brain of patients with AD and in the substantia nigra of patients with PD (Herradón and Pérez-García, 2014; Alguacil and Herradón, 2015), suggesting a modulatory role of PTN in these processes.