Serotonin causes an offset in the responses of PNs. (A) The DM2 and VM2 glomeruli (hatched white outline) and responses of these glomeruli to alcohols of increasing carbon chain length; C-6=3-hexanol, C-7=3-heptanol, C-8=3-octanol, C-9=3-nonanol, and C-10=3-decanol. (B) 5HT causes an offset of the odor-tuning curve of DM2 PNs. Responses to C-8 and C-9 were significantly higher in flies exposed to 5HT, compared to control flies (n=11 and 9, respectively; *P <0.05; **P <0.01). (C) Responses measured from the VM2 to C-7 were significantly higher in flies exposed to 5HT, compared to control flies (n=11 and 9, respectively; *P <0.05). Data in B and C are represented as mean±SEM. Scale bar=10 μm.