The Serotonergic Neurons of the CNS are not Necessary for Appetitive and Aversive Olfactory Learning.

<p>For testing appetitive olfactory learning, we utilized a two-group, reciprocal training design consisting of two half trials that give rise to a final performance index. Third instar larvae lacking serotonergic neurons preferred an odor that was paired with 2-M fructose (A, B). Using a single odor, non-reciprocal standard assay for aversive odor-shock learning third instar larvae lacking serotonergic neurons avoided the odor paired with pulses of electric shock (C, D). In both learning experiments, TRH-GAL4/UAS-<i>hid,rpr</i> larvae achieved relatively high performance scores (A) (p<0.01) (C) (p<0.001). Similar results were obtained for TPH-GAL4/UAS-<i>hid,rpr</i> larvae, which showed significant sugar learning (p<0.01) and electric shock learning (p<0.01). In none of the learning assays significant differences between experimental and control larvae were found. Under each boxplot of the figure for each genotype the sample size is shown; n = 10−16. Asterisks above each boxplot indicate, if the data is significantly different from zero. **<0.01; ***<0.001.