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Subcellular distributions of adenosine A 1 and A 2A receptors in the rat dorsomedial nucleus of the solitary tract at the level of the area postrema
Author(s) -
Pickel Virginia M.,
Chan June,
Linden Joel,
Rosin Diane L.
Publication year - 2006
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/syn.20326
Subject(s) - area postrema , solitary tract , receptor , neuroscience , adenosine , biology , axon , adenosine receptor , excitatory postsynaptic potential , neuropil , solitary nucleus , microbiology and biotechnology , chemistry , nucleus , endocrinology , inhibitory postsynaptic potential , central nervous system , biochemistry , agonist
Adenosine A 1 and A 2A receptors mediate distinct cardiovascular components of defense reactions that are ascribed, in part, to opposing actions within the nucleus tractus solitarius. To assess the cellular sites of relevance to these actions, we examined the light and electron microscopic immunolabeling of adenosine A 1 and A 2A receptors in the rat dorsomedial nucleus of the solitary tract at the level of the area postrema (dmNTS‐AP), a region crucial for cardiovascular regulation involving vagal baroreceptor afferents. Immunoreactivity for each receptor was independently localized to distinct segments of plasma membranes and endomembranes in somatodendritic, axonal, and glial profiles. The dendritic labeling for each receptor also was detected within and near asymmetric, excitatory‐type synapses. Of all peroxidase labeled profiles exclusive of somata, ∼58% were A 1 ‐ and 39% were A 2A ‐labeled dendrites. Dendrites and astrocytic glia were the profiles that most often expressed both subtypes of adenosine receptors. The axonal labeling for A 2A receptors was seen mainly in unmyelinated axons, whereas the A 1 receptors were prominently localized within axon terminals. These terminals often formed single or multisynaptic excitatory‐type junctions or single symmetric synapses on dendrites, a few of which expressed A 1 and A 2A receptors. These results provide the first ultrastructural evidence that A 1 and A 2A receptors have distributions conductive to their dual involvement in modulating the output of single neurons and glial function in the dmNTS‐AP, where the predominate presynaptic effects of adenosine are mediated through A 1 receptors. Synapse 60:496–509, 2006. © 2006 Wiley‐Liss, Inc.