Ultrastructural relations between beta-adrenergic receptors and catecholaminergic neurons.
We performed dual electron microscopic immunocytochemistry to determine the precise cellular relations between beta-adrenergic receptors (beta AR) and catecholaminergic terminals within adult rat brains. An antibody, beta AR404, against a peptide corresponding to the C-terminus of the hamster lung beta AR (beta 2 subtype) together with an anti-tyrosine hydroxylase (TH), a catecholaminergic marker, were used. Results show predominant labeling for beta AR404 within small astrocytic processes (beta-A). This is in sharp contrast to earlier results which showed neuronal labeling when using antibodies against the third intracellular loop of the receptor and of neurons-plus-astrocytes labeled using antibodies against the whole beta AR molecule. beta-A within visual cortex and nuclei of the solitary tracts frequently contacted blood vessel basement membrane and TH-immunoreactive terminals. TH-immunoreactive axons forming axo-axonic juxtapositions with non-TH terminals were also noted to be surrounded by beta-A. In the area postrema, a brain region lacking a blood-brain barrier, few beta-A occurred adjacent to TH-immunoreactive terminals or elsewhere. Thus, 1) catecholamines may act beyond morphologically identifiable synapses; 2) beta-A may mediate interactions between catecholamines and other transmitters; 3) there may be substantial heterogeneity in the structure or the conformation of the beta AR protein between neurons and glia or across CNS regions.
Aoki
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Center for Neural Science and Biology, New York University, New York 10003.
Pickel
V M
VM
D000595:Amino Acid Sequence; D000818:Animals; D001369:Axons / Q000502:physiology; D002395:Catecholamines / Q000502:physiology*; D006224:Cricetinae; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009474:Neurons / Q000648:ultrastructure*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000648:ultrastructure*; D014793:Visual Cortex / Q000502:physiology / Q000648:ultrastructure
D002395:Catecholamines; D011943:Receptors, Adrenergic, beta