Immunoreactive dopamine beta-hydroxylase in neuronal groups in the goldfish brain

Dopamine beta-hydroxylase immunoreactivity is visualized by immunocytochemical techniques for the first time in brainstem neurons of a teleost, the goldfish, Carassius auratus. Three anatomically separate populations of immunoreactive cells are elucidated: one group of moderately stained cells is identified in the isthmal tegmentum; a second group forms a continuous column of densely stained cells, lateral or dorsolateral to the medial longitudinal fasciculus from the midmedulla to the medullospinal transition zone, and a third group of densely stained cells is located dorsomedially in the postobecular region of the medulla. The location of these dopamine-beta-hydroxylase-immunoreactive neurons is similar to that in mammalian brains, i.e. in the locus coeruleus, lateral medullary tegmentum and area postrema. The presence of norepinephrine-synthesizing neurons in the above-listed brainstem regions of the goldfish provides further evidence for homologizing these nuclei to the same-named regions in mammalian brains.