Regional distribution and cellular localization of β2-adrenoceptors in the adult zebrafish brain (Danio rerio)

• Published in: Journal of comparative neurology (1911) 2010-05, Vol.518 (9), p.1418-1441
• Main Authors: Ampatzis, Konstantinos, Dermon, Catherine R.
• Format: Article
• Language: English
• Subjects: catecholamines; glia; hypothalamus; locus coeruleus; noradrenergic receptors; teleost fish
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.22278

The β2‐adrenergic receptors (ARs) are G‐protein‐coupled receptors that mediate the physiological responses to adrenaline and noradrenaline. The present study aimed to determine the regional distribution of β2‐ARs in the adult zebrafish (Danio rerio) brain by means of in vitro autoradiographic and immunohistochemical methods. The immunohistochemical localization of β2‐ARs, in agreement with the quantitative β‐adrenoceptor autoradiography, showed a wide distribution of β2‐ARs in the adult zebrafish brain. The cerebellum and the dorsal zone of periventricular hypothalamus exhibited the highest density of [3H]CGP‐12177 binding sites and β2‐AR immunoreactivity. Neuronal cells strongly stained for β2‐ARs were found in the periventricular ventral telencephalic area, magnocellular and parvocellular superficial pretectal nuclei (PSm, PSp), occulomotor nucleus (NIII), locus coeruleus (LC), medial octavolateral nucleus (MON), magnocellular octaval nucleus (MaON) reticular formation (SRF, IMRF, IRF), and ganglionic cell layer of cerebellum. Interestingly, in most cases (NIII, LC, MON, MaON, SRF, IMRF, ganglionic cerebellar layer) β2‐ARs were colocalized with α2A‐ARs in the same neuron, suggesting their interaction for mediating the physiological functions of nor/adrenaline. Moderate to low labeling of β2‐ARs was found in neurons in dorsal telencephalic area, optic tectum (TeO), torus semicircularis (TS), and periventricular gray zone of optic tectum (PGZ). In addition to neuronal, glial expression of β2‐ARs was found in astrocytic fibers located in the central gray and dorsal rhombencephalic midline, in close relation to the ventricle. The autoradiographic and immunohistochemical distribution pattern of β2‐ARs in the adult zebrafish brain further support the conserved profile of adrenergic/noradrenergic system through vertebrate brain evolution. J. Comp. Neurol. 518:1418–1441, 2010. © 2009 Wiley‐Liss, Inc.