ACE2 and nervous system disorder: Taken the lower brain expression of angiotensin-converting enzyme 2 (ACE2), relative to other tissues, ACE2, alone, cannot verify the incidence of neurological affection observed with COVID-19, and other mediators should be considered, of which orexins (OXs) were chosen based on multiple functional similarities with ACE2 and their implications in various neurological disorders that can be triggered by SARS-CoV-2 as well.