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Pro‐opiomelanocortin colocalizes with corticotropin‐ releasing factor in axon terminals of the noradrenergic nucleus locus coeruleus
Author(s) -
Reyes Beverly A. S.,
Glaser Julia D.,
Magtoto Ronaldo,
Van Bockstaele Elisabeth J.
Publication year - 2006
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2006.04744.x
Subject(s) - locus coeruleus , axon , immunoelectron microscopy , medicine , endocrinology , immunogold labelling , enkephalin , biology , opioid peptide , chemistry , microbiology and biotechnology , opioid , central nervous system , anatomy , immunohistochemistry , ultrastructure , receptor
We previously demonstrated that the opioid peptide enkephalin and corticotropin‐releasing factor (CRF) are occasionally colocalized in individual axon terminals but more frequently converge on common dendrites in the locus coeruleus (LC). To further examine potential opioid cotransmitters in CRF afferents we investigated the distribution of pro‐opiomelanocortin (POMC), the precursor that yields the potent bioactive peptide β‐endorphin, with respect to CRF immunoreactivity using immunofluorescence and immunoelectron microscopic analyses of the LC. Coronal sections were collected through the dorsal pontine tegmentum of rat brain and processed for immunocytochemical detection of POMC and CRF or tyrosine hydroxylase (TH). POMC‐immunoreactive processes exhibited a distinct distribution within the LC as compared to the enkephalin family of opioid peptides. Specifically, POMC fibers were enriched in the ventromedial aspect of the LC with fewer fibers present dorsolaterally. Immunofluorescence microscopy showed frequent coexistence of POMC and CRF in varicose processes that overlapped TH‐containing somatodendritic processes in the LC. Ultrastructural analysis showed POMC immunoreactivity in unmyelinated axons and axon terminals. Axon terminals containing POMC were filled with numerous large dense‐core vesicles. In sections processed for POMC and TH, ∼ 29% of POMC‐containing axon terminals ( n = 405) targeted dendrites that exhibited immunogold–silver labeling for TH. In contrast, sections processed for POMC and CRF showed that 27% of POMC‐labeled axon terminals ( n = 657) also exhibited CRF immunoreactivity. Taken together, these data indicate that a subset of CRF afferents targeting the LC contain POMC and may be positioned to dually impact LC activity.