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β‐Adrenergic receptors primarily are located on the dendrites of granule cells and interneurons but also are found on astrocytes and a few presynaptic profiles in the rat dentate gyrus
Author(s) -
Milner Teresa A.,
Shah Prakriti,
Pierce Joseph P.
Publication year - 2000
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/(sici)1098-2396(20000601)36:3<178::aid-syn3>3.0.co;2-6
Subject(s) - dentate gyrus , dendritic spine , granule cell , axon , postsynaptic potential , chemistry , granule (geology) , excitatory postsynaptic potential , neuroscience , biology , biophysics , microbiology and biotechnology , receptor , hippocampal formation , inhibitory postsynaptic potential , biochemistry , paleontology
In the rat dentate gyrus, β‐adrenergic receptor (β‐AR) activation is thought to be important in mediating the effects of norepinephrine (NE). β‐AR‐immunoreactivity (β‐AR‐I) was localized in this study by light and electron microscopy in the rat dentate gyrus by using two previously characterized antibodies to the β‐AR. By light microscopy, dense β‐AR‐I was observed in the somata of granule cells and a few hilar interneurons. Diffuse and slightly granular β‐AR‐I was found in all laminae, although it was most noticeable in the molecular layer. Ultrastructurally, the cytoplasm of granule cell and interneuronal perikarya (some of which contained parvalbumin immunoreactivity) contained β‐AR‐I. β‐AR‐I was associated primarily with the endoplasmic reticula; however, a few patches were observed near the plasmalemma. Quantitative analysis revealed that the greatest proportion of β‐AR‐labeled profiles was found in the molecular layer. The majority of β‐AR‐labeled profiles were either dendritic or astrocytic. In dendritic profiles, β‐AR‐I was prominent near postsynaptic densities in large dendrites, many of which originated from granule cell somata. Moreover, some β‐AR‐I was found in dendritic spines, sometimes affiliated with the spine apparati. Astrocytic profiles with β‐AR‐I were commonly found next to unlabeled terminals which formed asymmetric (excitatory‐type) synapses with dendritic spines. Additionally, β‐AR‐I was observed in a few unmyelinated axons and axon terminals, many of which formed synapses with dendritic spines. Dual‐labeling studies revealed that axons and axon terminals containing tyrosine hydroxylase (TH), the catecholamine synthesizing enzyme, often were near both neuronal and glial profiles containing β‐AR‐I. These studies demonstrate that hippocampal β‐AR‐I is localized: 1) principally in postsynaptic sites on granule cells and a few interneurons (some of which were basket cells); and 2) in glial processes. These observations add further support to the contention that β‐AR‐activation modulates synaptic function through disparate pathways: directly, at either postsynaptic densities or presynaptic processes, or indirectly, through adjacent glial processes. Synapse 36:178–193, 2000. © 2000 Wiley‐Liss, Inc.