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

Abstract

The beta(2)-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 beta(2)-ARs in the adult zebrafish (Danio rerio) brain by means of in vitro autoradiographic and immunohistochemical methods. The immunohistochemical localization of beta(2)-ARs, in agreement with the quantitative beta-adrenoceptor autoradiography, showed a wide distribution of beta(2)-ARs in the adult zebrafish brain. The cerebellum and the dorsal zone of periventricular hypothalamus exhibited the highest density of [(3)H]CGP-12177 binding sites and beta(2)-AR immunoreactivity. Neuronal cells strongly stained for beta(2)-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) beta(2)-ARs were colocalized with alpha(2A)-ARs in the same neuron, suggesting their interaction for mediating the physiological functions of nor/adrenaline. Moderate to low labeling of beta(2)-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 beta(2)-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 beta(2)-ARs in the adult zebrafish brain further support the conserved profile of adrenergic/noradrenergic system through vertebrate brain evolution.

Beta receptor-mediated modulation of the late positive potential in humans

“…A possible explanation for this interaction between propranolol and trait anxiety is that propranolol decreases tonic LC activity through actions at β2-receptors in the LC (Ampatzis and Dermon 2010; Berridge and Waterhouse 2003). Depending on a subject's baseline level of tonic LC activity (which correlates with trait anxiety), this shifts the subject to a higher or lower point on the inverted U curve describing the strength of phasic LC responses (which according to our proposal underlie LPP generation) as a function of tonic LC activity.…”

Sexual dimorphisms in swimming behavior, cerebral metabolic activity and adrenoceptors in adult zebrafish (Danio rerio)

“…To label the α 2 -ARs and β-ARs, in vitro autoradiography was applied [34,35,36], using the antagonists [ 3 H]-RX821002 (for α 2 -AR; 54Ci/mol, Amersham, UK) and Following incubation, free radioligand was removed by two washes in ice-cold TrisHCl buffer (5 and 10 minutes), and then sections were dried in a cold air stream.…”

“…Indeed, adrenoceptors are known to display sex dimorphic pattern in brain areas of avian [31,32] and mammalian [33] species. Recent evidence suggests that, zebrafish brain α 2 -and β-ARs [34,35] share similar characteristics with other teleosts [36], amphibians [37], birds [38,39] and mammals [40,41].…”

The development and general morphology of the telencephalon of actinopterygian fishes: synopsis, documentation and commentary

“…The zebrafish, Danio rerio is a remarkable case in point. This species, which is easy to breed, is currently used in a variety of neurogenetic studies, and is therefore proclaimed to be a model species (Ampatzis and Dermon 2010; Friedrich et al 2010; Kastenhuber et al 2010; Mueller et al 2004; Wullimann and Mueller 2004). However, in none of the zebrafish studies that have yet come to my attention, the location of the taeniae has been established.…”