Histological Structure of the Central Nervous System in Adult Zebrafish (Danio Rerio)

The increasing popularity of zebrafish in the field of scientific research makes a good knowledge of its anatomy and histology essential. The detailed knowledge of the zebrafish neuroanatomy is a valuable tool in its studies on the nervous system, allowing the changes made at various levels to be easily detected. 20 adult zebrafish were taken in our study from which histological sections of the brain were obtained. The most rostral telencephalic divisions are the pair of olfactory bulbs. The rest of the telencephalon is composed of two subdivisions: the dorsalis area and the ventralis telencephali area. The diencephalon comprises a total of 5 major regions that are organized dorso-ventrally in the adult brain. These are: epitalamus, dorsal thalamus, ventral thalamus, posterior tubercle and hypothalamus. The mesencephalon includes dorsal and ventral optic tectum (TeO), torus semicircularis and tegmentum. TeO is the most complex stratified structure in the brain of zebrafish. The rhombencephalon is often divided into a rostral metencephalon and a caudal myelencephalon. With the exception of the cerebellum, the rest of the ventral part of the metencephalon can only be arbitrarily separated from the more caudal myelencephalic portion of the medulla oblongata. Medulla oblongata and tegmentum are considered to make the brain stem. The first spinal roots, dorsal and ventral, are located caudally from Haller's very small commissure. The second dorsal root is located caudally at 500-800 mm. Currently, the use of this animal model is augmenting considerably in the research of neurological and neurodegenerative diseases in humans, due to its notable easier husbandry and breeding, but more important, genetic similarity with human.