The number of Tph-ir neurons for each genotype within different subregions of the DR at five rostrocaudal levels. DR subregions are organized by row, and anatomical levels are organized in columns from rostral (left) to caudal (right). Distance from bregma is indicated above each column in millimeters. N = 7–8 WT, n = 6–8 Fgfr1 HET, n = 7 Fgf8 HET, n = 9–10 Fgfr1/Fgf8 HET; *p < 0.05 vs. WT; bars represent the mean ± SEM. Abbreviations: DRD, dorsal raphe nucleus, dorsal part; DRC, dorsal raphe nucleus, caudal part; DRV, dorsal raphe nucleus, ventral part; DRVL/VLPAG, dorsal raphe nucleus, ventrolateral part/ventrolateral periaqueductal gray; DRI, dorsal raphe nucleus, interfascicular part.