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Serotonergic Innervation of Spinal Interneurons Synaptically Coupled with Phrenic and Intercostal Motor Pools
Author(s) -
GonzalezRothi Elisa,
Ross Heather,
Armstrong Gregory,
Streeter Kristi,
Cerreta Anthony,
Reier Paul,
Fuller David
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.659.7
Subject(s) - spinal cord , serotonergic , respiratory system , phrenic nerve , receptor , neuroscience , anatomy , biology , intercostal nerves , motor neuron , serotonin , medicine
Spinal serotonin (5‐HT) receptor activation is both necessary and sufficient to trigger persistent increases in respiratory output. While there is a prevalence of interneurons synaptically integrated into the phrenic and intercostal circuits, it is unknown whether these cells are innervated by 5‐HT and/or express relevant receptors. Accordingly, we investigated 5‐HT innervation and receptor expression of respiratory interneurons in the cervical and thoracic spinal cord. Pseudorabies virus, a retrograde transynaptic tracer, was applied to the diaphragm of adult female Sprague‐Dawley rats to identify phrenic and rostral intercostal motoneurons and synaptically antecedent interneurons. Using immunohistochemical dual‐labeling techniques we confirmed extensive 5‐HT immunoreactivity within the immediate vicinity of phrenic and intercostal motoneurons, as well as robust immunoreactivity near pre‐motor interneurons of both motor pools. Additionally, robust 5‐HT 2a , 5‐HT 2c , and 5‐HT 7 receptor immunoreactivity was also observed for both phrenic and intercostal pre‐motor interneurons in laminae VII and X. Protein and mRNA analyses confirmed receptor expression, and indicated regional differences in 5‐HT innervation and receptor expression in cervical vs. thoracic spinal cords. We conclude that respiratory pre‐motor interneurons in the cervical and thoracic spinal cords are innervated by 5‐HT and express receptors that have been previously implicated in triggering spinal respiratory neuroplasticity.