Optogenetic stimulation of PBel CGRP neurons is sufficient to mimic LiCl-induced CTA. A, Paradigm used to cause CTA. B, Pairing LiCl with novel tastant causes CTA (n = 8 mice per condition). C, Daily exposure to novel tastant 5 d before exposure to LiCl prevents CTA (n = 8 mice per condition). D, Daily exposure to LiCl 5 d before exposure to novel tastant prevents CTA (n = 8 mice per condition). E, Placement of fiber-optic implant in the PBN in a Calca^Cre/+ animal injected with AAV-DIO-ChR2-mCherry. F, Pairing photostimulation of PBel CGRP neurons with novel tastant causes CTA (n = 9 mice per condition). G, Daily exposure to PBel CGRP photostimulation 5 d before exposure to novel tastant prevents CTA (n = 9 mice per condition). H, Daily exposure to LiCl 5 d before exposure to novel tastant prevents PBel CGRP neuron-mediated CTA (n = 9 mice per condition). All values represent the mean ± SEM. **p < 0.001; ***p < 0.0001 (Bonferroni post hoc test between conditions).