ORGANIZATION OF THE OLFACTORY SYSTEM IN THE ADULT ZEBRAFISH - HISTOLOGICAL, IMMUNOHISTOCHEMICAL, AND QUANTITATIVE-ANALYSIS

The zebrafish, Danio rerio, is becoming an important model system for developmental studies. We have used a variety of histological techniqu es to characterize the adult structure of the olfactory system in this teleost to form a base for future developmental work. The olfactory e pithelium in this fish contains ciliated and microvillar sensory neuro ns, microvillar supporting cells, secretory goblet cells, and basal ce lls, and the adjacent nonsensory epithelium contains ciliated supporti ng cells. The olfactory bulb is a diffusely organized structure with f our laminae: olfactory nerve, glomerular, mixed mitral cell/plexiform, and granule cell layers. These structures and the synapses observed i n the olfactory bulb are typical of what is found in other vertebrates . We also examined the distribution of several neurotransmitter marker s (tyrosine hydroxylase, neuropeptide Y, dopamine-beta-hydroxylase, an d serotonin) in the olfactory bulb. Antibodies to neuropeptide Y, dopa mine-beta-hydroxylase, and serotonin labeled fibers in the olfactory b ulb and cell bodies in caudal regions of the brain in distributions co mparable to other species. Tyrosine hydroxylase immunoreactivity was o bserved in a set of intrinsic bulb neurons with extensive processes in the glomerular layer. In addition, the structural proteins glial fibr illary acidic protein and vimentin have distributions similar to those in the olfactory bulbs of other animals. Thus, the adult olfactory st ructures are analogous to the structures in other vertebrate animals i n morphology and chemical neuroanatomy. This similarity, along with it s numerous advantages for developmental studies, makes the zebrafish a good model for studies of olfaction and forebrain maturation. (C) 199 5 Wiley-Liss, Inc.