Fig. 7: Axons of dopaminergic NPFR^ENS neurons connect to the SEZ and AL regions in the brain.

a NPFR^ENS neurons are labeled by nSyt::GFP (green, axons) and Denmark (red, dendrites). 24 flies were examined. b Food intake of flies expressing RNAi against key factors for the synthesis and function of different neurotransmitters in NPFR^ENS neurons. Red-dash line box indicates expressing RNAi lines against two key enzymes for the synthesis of dopamine (DA) significantly increases the food intake. c NPFR^ENS neurons (NPFR^ENS-Gal4 > mCD8:RFP, red) are co-labeled with the dopaminergic neuron marker Ddc-LexA>myr:GFP. Note they have the same dendritic pattern in the SEZ region. The white dashed box frames the cell body of NPFR^ENS neurons, with magnified views in the lower right corner. 23 flies were examined. d NPFR^ENS neurons (NPFR^ENS-Gal4 > mCD8:GFP, green) stained positive for Tyrosine hydroxylase (TH, red). 15 flies were examined. e Trans-tango experiment shows that NPFR^ENS neurons are synaptically connected with neurons (red, HA staining) in the subesophageal zone (SEZ) and antennal lobe (AL). 25 flies were examined. f Proposed model of EEC sensing of L-Glu and its downstream circuit. L-Glu sensing by EECs inhibits NPF secretion from EECs by slowing down Ca²⁺ oscillations, thereby blocking the activation of dopaminergic NPFR⁺ enteric neurons that inhibit feeding. Data are represented as mean ± SD. Significance was determined using two-sided unpaired t-test. n, number of groups performed for quantification of food intake, 5 flies in each group b. Source data are provided as a Source Data file. Scale bars are indicated in panels.