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Adrenergic beta receptors are not uniformly distributed in the cerebellar cortex
Author(s) -
Sutin Jerome,
Minneman Kenneth P.
Publication year - 1985
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.902360410
Subject(s) - iodocyanopindolol , receptor , biology , cerebellum , adrenergic receptor , purkinje cell , cerebellar cortex , practolol , medicine , beta (programming language) , endocrinology , propranolol , biophysics , biochemistry , agonist , intrinsic activity , computer science , programming language
The noradrenergic (NE) innervation of the cerebellar cortex is sparse, forming a broad plexus of radially oriented axons distributing throughout the granular and molecular layers. Autoradiographic studies of beta‐adrenergic receptor distribution in the rat show the greatest density of silver grains in the molecular layer (Palacios and Kuhar, 1982). In the course of studies of NE hyperinnervated structures, we found that beta receptors are nonhomogeneously distributed in the Purkinje cell layer, where they occur in “patches” overlying small groups of Purkinje cell somata. Tissue sections were incubated in 10 pM 125 iodocyanopindolol (ICYP), which binds equally to beta 1 and beta 2 adrenergic receptors. Nonspecific binding was determined in sections incubated in 125 ICYP and 1 μM dl‐propranolol. Beta‐adrenergic receptor patches are of irregular size and are most prominent in the vermis of lobules I‐IX, although the medial cerebellar hemispheres also show areas of increased silver grains over Purkinje cells. In order to determine the subtype of beta receptors, adjacent sections were incubated with either 125 ICYP and the beta 2 ‐selective antagonist IPS‐339, or 125 ICYP and the beta 1 ‐selective antagonist practolol. Patches were observed after each incubation procedure, indicating that they are composed of both beta 1 and beta 2 receptors. Patches are observed in normal animals and also in rats in which cerebellar NE content was increased 165% by neonatal treatment with 6‐hydroxydopamine. This treatment does not alter the density of beta receptors. The cerebellar elements in which the beta receptors are located is not known. While silver grains accumulate over small groups of Purkinje cell somata, they are not coextensive with these cell bodies. The distribution of beta‐adrenergic receptors does not parallel the arrangement of noradrenergic varicosities in the rat cerebellar cortex.