The adult central nervous cholinergic system of a neurogenetic model animal, the zebrafish Danio rerio.

The central nervous cholinergic system of the zebrafish (Danio rerio), a model animal for neurogenetics, is documented here using immunohistochemical methods for visualizing choline acetyltransferase (ChAT), the acetylcholine synthesizing enzyme. Neuronal cell bodies containing ChAT are present in the telencephalon (lateral nucleus of ventral telencephalic area), preoptic region (anterior/posterior parvocellular and magnocellular preoptic nuclei), diencephalon (habenula, dorsal thalamus, posterior tuberculum), mesencephalon (Edinger-Westphal (EW) nucleus, oculomotor nerve nucleus, rostral tegmental nucleus, tectal type XIV neurons), isthmic region (nucleus lateralis valvulae, secondary gustatory-viscerosensory nucleus, nucleus isthmi (NI), perilemniscal nucleus, superior reticular nucleus (SRN)) and rhombencephalon (trochlear, trigeminal, abducens, facial, glossopharyngeal-vagal motor nerve nuclei, rostral and caudal populations of octavolateralis efferent neurons). In addition, some ChAT positive neurons are present in the rhombencephalic reticular formation, the central gray, and in cells accompanying the descending trigeminal tract. Obvious ChAT positive terminal fields are present in the supracommissural nucleus of area ventralis telencephali and the medial zone of area dorsalis telencephali, parvocellular superficial pretectal nucleus, torus semicircularis, medial octavolateralis nucleus, facial, glossopharyngeal, and vagal lobes, and in the inferior lobe (around the periventricular nucleus of the lateral recess and in the diffuse nucleus). The identification of all central nervous cholinergic systems provided here in this model system is pivotal for future detailed studies of their development and maintenance, e.g., with regard to the zebrafish ventral telencephalic and isthmic superior reticular neuronal populations, likely representing the homologues of at least part of the cholinergic basal forebrain and pedunculopontine/laterodorsal tegmental ascending activating systems of mammals, respectively.