Fig. 8

Dorsal accumulation of dopaminergic neurons in the adult amphioxus brain. a–f Neurons detected by immunohistochemistry with an antibody directed against tyroxine hydroxylase and shown in frontal thick vibratome sections ordered from anterior to posterior. The most anterior dopaminergic neurons are slightly posterior to the most anterior glutamatergic and GABAergic neurons, which are located at the level of the neuropore, as shown in Figs. 6d and 7h (sections at the same level as a). The dorsal domain of dopaminergic neurons starts at the level of b, equivalent to Figs. 6e and 7i for glutamatergic and GABAergic neurons, respectively, and broadens posteriorly with a more prominent dorsal cluster at the level of the infundibular organ, which is visible in f (asterisk). Colour code: red, TH; green, neuropil and intraventricular cilia (acetylated tubulin); blue/cyan, nuclear staining (Dapi)