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Ultrastructural evidence for prominent postsynaptic localization of α 2C ‐adrenergic receptors in catecholaminergic dendrites in the rat nucleus locus coeruleus
Author(s) -
Lee Amy,
Rosin Diane L.,
Van Bockstaele Elisabeth J.
Publication year - 1998
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/(sici)1096-9861(19980504)394:2<218::aid-cne6>3.0.co;2-5
Subject(s) - biology , catecholaminergic , locus coeruleus , axon , immunolabeling , neuropil , ultrastructure , postsynaptic potential , tyrosine hydroxylase , neuroscience , synaptic vesicle , medicine , endocrinology , microbiology and biotechnology , nucleus , dopamine , receptor , anatomy , central nervous system , vesicle , biochemistry , immunohistochemistry , membrane , immunology
Alpha‐2‐adrenergic receptor (α 2 ‐AR) agonists potently inhibit the activity of noradrenergic neurons of the locus coeruleus (LC), an effect that may be mediated by the A‐ and/ or C‐subtypes of α 2 ‐AR (α 2A ‐ and α 2C ‐AR). To gain insight into the functional significance of these α 2 ‐AR subtypes in the LC, we have examined their ultrastructural localization by using subtype‐specific antibodies. We recently demonstrated that α 2A ‐ARs are localized prominently in axon terminals and catecholaminergic dendrites in the LC. In the present study, we sought to identify the subcellular substrates underlying α 2C ‐AR actions in the LC by analyzing the ultrastructural distribution of α 2C ‐AR immunoreactivity (α 2C ‐AR‐IR) in sections that were dually labeled for the catecholamine‐synthesizing enzyme tyrosine hydroxylase (TH). Alpha‐2C‐AR‐IR was predominantly localized in dendrites, most of which also contained immunolabeling for TH. Within such dendrites, α 2C ‐AR‐IR was associated with the plasma membrane and occasionally Golgi cisternae and tubulovesicles. The vast majority of dendrites containing α 2C ‐AR‐IR received asymmetric (excitatory) contacts from unlabeled axon terminals that often contained dense core vesicles. Alpha‐2C‐AR‐IR was observed in some unmyelinated axons and astrocytic processes that were apposed to TH‐immunoreactive dendrites but was rarely associated with axon terminals. These results provide the first ultrastructural evidence that α 2C ‐ARs (1) are localized postsynaptically in catecholaminergic neurons of the LC and (2) may be strategically situated to modulate the activation of LC neurons by excitatory inputs. J. Comp. Neurol. 394:218–229, 1998. © 1998 Wiley‐Liss, Inc.