Cholinergic elements in the zebrafish central nervous system: Histochemical and immunohistochemical analysis

Abstract

Recently, the zebrafish has been extensively used for studying the development of the central nervous system (CNS). However, the zebrafish CNS has been poorly analyzed in the adult. The cholinergic/cholinoceptive system of the zebrafish CNS was analyzed by using choline acetyltransferase (ChAT) immunohistochemistry and acetylcholinesterase (AChE) histochemistry in the brain, retina, and spinal cord. AChE labeling was more abundant and more widely distributed than ChAT immunoreactivity. In the telencephalon, ChAT-immunoreactive (ChAT-ir) cells were absent, whereas AChE-positive neurons were observed in both the olfactory bulb and the telencephalic hemispheres. The diencephalon was the region with the lowest density of AChE-positive cells, mainly located in the pretectum, whereas ChAT-ir cells were exclusively located in the preoptic region. ChAT-ir cells were restricted to the periventricular stratum of the optic tectum, but AChE-positive neurons were observed throughout the whole extension of the lamination except in the marginal stratum. Although ChAT immunoreactivity was restricted to the rostral tegmental, oculomotor, and trochlear nuclei within the mesencephalic tegmentum, a widespread distribution of AChE reactivity was observed in this region. The isthmic region showed abundant AChE-positive and ChAT-ir cells in the isthmic, secondary gustatory and superior reticular nucleus and in the nucleus lateralis valvulae. ChAT immunoreactivity was absent in the cerebellum, although AChE staining was observed in Purkinje and granule cells. The medulla oblongata showed a widespread distribution of AChE-positive cells in all main subdivisions, including the octavolateral area, reticular formation, and motor nuclei of the cranial nerves. ChAT-ir elements in this area were restricted to the descending octaval nucleus, the octaval efferent nucleus and the motor nuclei of the cranial nerves. Additionally, spinal cord motoneurons appeared positive to both markers. Substantial differences in the ChAT and AChE distribution between zebrafish and other fish species were observed, which could be important because zebrafish is widely used as a genetic or developmental animal model.

Connections of thalamic modulatory centers to the vocal control system of the zebra finch

“…However, our results, as well as others using the Ab from the same source (19), show that very little, if any, ChAT-IR occurs in any telencephalic song system nuclei, including the HVC, to which the VP cells of the BF are supposed to send cholinergic fibers (12). Previous studies in a wide variety of animals, including zebra finches (19), pigeons (20), and zebra fish (21), have shown that there can be considerable mismatches between ChAT-IR and AChE histochemistry, as well as between transmitter levels and their receptors (20). AChE has also been seen in noncholinergic areas of the brain and has been shown to be important in degrading other neuropeptides as well as AChE (22,23,24).…”

Scopolamine-induced learning impairment reversed by physostigmine in zebrafish

“…Similarly, carbachol has been shown to suppress evoked field potential responses in the hippocampal and entorhinal areas of the rat (Yun et al, 2000). Histologically, neurons containing AChE were detected in most areas of the central nervous system, including the olfactory bulb, telencephalon, cerebellum, medulla oblongata, and spinal cord (Clemente et al, 2004). In particular, the telencephalon, which is thought to be responsible for learning in teleost fishes such as zebrafish and goldfish (Portavella et al, 2002;Rodriguez et al, 2002), appeared to have AChE-positive neurons in various nuclei of the dorsal and ventral areas.…”

A genetic model of amyotrophic lateral sclerosis in zebrafish displays phenotypic hallmarks of motoneuron disease

“…ChAT immunohistochemistry was performed as described (Clemente et al, 2004). Briefly, fresh frozen sections (20 m) of spinal cord were collected from end-stage fish that had been fixed in 4% RESOURCE ARTICLE PFA in 0.1 M phosphate buffer (PB) (pH 7.4) for 10 minutes.…”