TPH2, Mash1, and 5-HT were mainly expressed in neurons but rarely expressed in astrocytes or microglia in the piriform cortex (Pir), while they were not overlapping in the other cerebral regions, implying that the neurons in Pir might be involved in the role of 5-HT in ALS. Here, ASCL1 is linked to amyotrophic lateral sclerosis.