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Activation of nucleus tractus solitarii (nTS) neurons that project to the rostral ventrolateral medulla (RVLM) or hypothalamic paraventricular nucleus (PVN): Role of acute hypoxia (AH)
Author(s) -
Ruyle Brian C,
Heesch Cheryl M,
King T Luise,
Kline David D,
Hasser Eileen M
Publication year - 2012
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.26.1_supplement.702.15
Subject(s) - rostral ventrolateral medulla , catecholaminergic cell groups , medicine , nucleus , endocrinology , catecholaminergic , tyrosine hydroxylase , chemistry , solitary nucleus , hypoxia (environmental) , medulla oblongata , hypothalamus , neuroscience , central nervous system , biology , catecholamine , immunohistochemistry , oxygen , organic chemistry
The nTS integrates chemoafferent input regarding blood oxygen levels and sends projections to the RVLM and PVN. The relative activation by AH of the nTS‐RVLM versus the nTS‐PVN pathway is unknown. We hypothesized that the nTS‐PVN pathway is relatively inactive during mild‐moderate AH but increases its activity with severe AH, while the nTS‐RVLM pathway is maximally activated by mild‐moderate hypoxia. Retrograde tracers were microinjected into the PVN or RVLM to identify nTS neurons that project to these regions. Following recovery, conscious rats were subjected to Normoxia (21% O2) or AH (12 or 10% O2). We used Fos‐immunoreactivity (IR) as an index of neuronal activation and Tyrosine Hydroxylase (TH)‐IR to identify catecholaminergic neurons. AH produced an intensity‐dependent increase in ventilation and Fos‐IR in nTS cells (O2: 21%, 10±4; 12%, 54±14; 10%, 100±28 cells). Increasing AH severity (from 12% to 10% O2) increased the percentage of activated nTS‐PVN cells but not nTS‐RVLM cells. Very few nTS‐RVLM cells (4±1%) were TH‐IR. In contrast, 40±7% nTS‐PVN cells were TH‐IR; Fos‐IR in these neurons increased with AH severity. Results suggest AH progressively increases the activity of nTS‐PVN neurons; many of these cells are catecholaminergic. In contrast, nTS‐RVLM neurons are activated by mild‐moderate AH and undergo little further activation with increased severity of hypoxia. Multi‐Investigator HL98602