Figure 1.

Serotonergic neuron activity was modulated by expressing TrpA1 in specific sets of serotonin neurons (top panel). Place memory levels were tested at 24°C. The necessity of serotonergic neurons was tested by expressing the tetanus toxin light chain (TNT) in these neurons (middle panel). Flies of different genotypes were exposed to 41°C, trained with 30°C and tested at 24°C. The sufficiency of the serotonergic neurons and subsets were examined (lower panel). Serotonin neuron activity was increased by expressing and activating TrpA1 or TrpM8 in specific neurons. Flies were trained at 30°C and tested at 24°C.