Fig. 3

The histaminergic system. A and B, Ventral views of whole-mount 6 dpf larval brains, anterior to the top, processed for histamine (HA) immunostaining. Histamine-immunoreactive neurons in the posterior hypothalamus with descending and ascending fibre projections in the brain of a vmat2^+/+ larva and decreased immunoreactive to histamine in the hypothalamus of a vmat2^−/− larva. Scale bar = 75 µm. C and D, Ventral views of whole-mount 6 dpf larval brains, anterior to the top, processed for hdc RNA in situ hybridisation (ISH). Scale bar = 75 µm. E and F, Dorsal views of whole-mount 6 dpf larval brains, anterior to the top, processed for hrh1 RNA in situ hybridisation (ISH). n= 5 for each genotype. Scale bar = 75 µm. G, Bar chart showing results of histamine-immunoreactive cells counting on larval brains of the indicated genotype at 6 dpf. The number of histaminergic neurons was significantly reduced in the vmat2^−/− brains. n = 10 for each genotype. H, Bar chart showing results of hdc-positive cells counting on larval brains of the indicated genotype. The number of hdc-positive cells was significantly increased in the vmat2^−/− brains. n = 6 for each genotype. I, Bar chart showing results of high-performance liquid chromatography (HPLC) assay on larvae of the indicated genotype at 6 dpf. Histamine level was significantly decreased in vmat2^−/− larvae. n= 6 for each genotype. J, Bar chart showing results of reverse transcription-quantitative PCR (RT-qPCR) assays on larvae of the indicated genotype at 6 dpf. Vmat2^−/− and vmat2^+/+ did not show a significant difference in the amount of hrh1 transcript. n= 5 for each genotype. Data are mean ± SEM. Student's t test was used for statistical analysis. *P < .05. ^‡P < .001