Comparative anatomy of α₂ and β adrenoceptors in the adult and developing brain of the marine teleost the red porgy (Pagrus pagrus, Sparidae): [³H]clonidine and [³H]dihydroalprenolol quantitative autoradiography and receptor subtypes immunohistochemistry

Abstract

The present study aimed to determine the anatomic distribution and developmental profile of alpha(2) and beta adrenoceptors (AR) in marine teleost brain. Alpha 2 and beta adrenoceptors were studied at different developmental stages by using [(3)H]clonidine and [(3)H]dihydroalprenolol, respectively, by means of in vitro quantitative autoradiography. Furthermore, immunohistochemical localization of the receptor subtypes was performed to determine their cellular distribution. Saturation studies determined a high-affinity component of [(3)H]clonidine and [(3)H]dihydroalprenolol binding sites. High levels of both receptors were found in preglomerular complex, ventral hypothalamus, and lateral torus. Dorsal hypothalamus and isthmus included high levels of alpha(2) AR, whereas pretectum and molecular and proliferative zone of cerebellum were specifically characterized by high densities of beta AR. From the first year of life, adult levels of both AR were found in most medial telencephalic, hypothalamic, and posterior tegmental areas. Decreases in both receptors densities with age were prominent in ventral and posterior telencephalic, pretectal, ventral thalamic, hypothalamic, and tegmental brain regions. Immunohistochemical data were well correlated with autoradiography and demonstrated the presence of alpha(2A), alpha(2C), beta(1), and beta(2) AR subtype-like immunoreactivity. Both the neuronal (perikaryal or dendritic) and the glial localization of receptors was revealed. The localization and age-dependent alterations in alpha(2) and beta AR were parallel to plasticity mechanisms, such as cell proliferation in periventricular thalamus, hypothalamus, and cerebellum. In addition, the biochemical characteristics, distribution pattern, and neuronal or glial specificity of the receptors in teleost brain support a similar profile of noradrenergic transmission in vertebrate brain evolution.

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

“…The adrenoceptor binding parameters support that zebrafish α 2 -and β-adrenoceptors have similar properties to those in mammals, although the Bmax values determined were lower than those in land vertebrates [38,41), but similar to those reported for the teleost Pagrus pagrus [36].…”

“…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].…”

Catecholaminergic connectivity to the inner ear, central auditory, and vocal motor circuitry in the plainfin midshipman fish porichthys notatus

“…, 2008). Similar distributions of ARs are found in a marine species, the red porgy, although hindbrain nuclei are not reported (Zikopoulos and Dermon, 2005).…”

Ovulation and spawning induction in Caspian kutum Rutilus frisii kutum by administration of GnRHa and catecholaminergic pharmaceutical compounds with Ovaprim

“…In fact, many dopaminergic drugs (DA agonists) are relatively strong antagonists at the a 1 and/or a 2 adrenergic receptors (Hommer, Zahn, Pickar & Van Kammen 1984). Other researchers have reported that adrenergic receptors were extremely expressed in the hypothalamus, as previously suggested for teleost fish, and thus hypothalamic adrenergic receptors involved in gonadotropinreleasing control, sexual differentiation and reproductive behaviour regulation in fish (Ruuskanen, Peitsaro, Kaslin, Panula & Scheinin 2005;Zikopoulos & Dermon 2005;Ampatzis et al 2008).…”