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Catecholaminergic neurons projecting to the paraventricular nucleus of the hypothalamus are essential for cardiorespiratory adjustments to hypoxia.
- Source :
-
American journal of physiology. Regulatory, integrative and comparative physiology [Am J Physiol Regul Integr Comp Physiol] 2015 Oct; Vol. 309 (7), pp. R721-31. Date of Electronic Publication: 2015 Jul 08. - Publication Year :
- 2015
-
Abstract
- Brainstem catecholamine neurons modulate sensory information and participate in control of cardiorespiratory function. These neurons have multiple projections, including to the paraventricular nucleus (PVN), which contributes to cardiorespiratory and neuroendocrine responses to hypoxia. We have shown that PVN-projecting catecholaminergic neurons are activated by hypoxia, but the function of these neurons is not known. To test the hypothesis that PVN-projecting catecholamine neurons participate in responses to respiratory challenges, we injected IgG saporin (control; n = 6) or anti-dopamine β-hydroxylase saporin (DSAP; n = 6) into the PVN to retrogradely lesion catecholamine neurons projecting to the PVN. After 2 wk, respiratory measurements (plethysmography) were made in awake rats during normoxia, increasing intensities of hypoxia (12, 10, and 8% O2) and hypercapnia (5% CO2-95% O2). DSAP decreased the number of tyrosine hydroxylase-immunoreactive terminals in PVN and cells counted in ventrolateral medulla (VLM; -37%) and nucleus tractus solitarii (nTS; -36%). DSAP produced a small but significant decrease in respiratory rate at baseline (during normoxia) and at all intensities of hypoxia. Tidal volume and minute ventilation (VE) index also were impaired at higher hypoxic intensities (10-8% O2; e.g., VE at 8% O2: IgG = 181 ± 22, DSAP = 91 ± 4 arbitrary units). Depressed ventilation in DSAP rats was associated with significantly lower arterial O2 saturation at all hypoxic intensities. PVN DSAP also reduced ventilatory responses to 5% CO2 (VE: IgG = 176 ± 21 and DSAP = 84 ± 5 arbitrary units). Data indicate that catecholamine neurons projecting to the PVN are important for peripheral and central chemoreflex respiratory responses and for maintenance of arterial oxygen levels during hypoxic stimuli.<br /> (Copyright © 2015 the American Physiological Society.)
- Subjects :
- Animals
Blood Pressure physiology
Brain Stem cytology
Brain Stem physiology
Dopamine beta-Hydroxylase antagonists & inhibitors
Heart Rate physiology
Hypercapnia physiopathology
Immunohistochemistry
Male
Paraventricular Hypothalamic Nucleus cytology
Rats
Rats, Sprague-Dawley
Reflex physiology
Ribosome Inactivating Proteins, Type 1 pharmacology
Saporins
Telemetry
Catecholamines physiology
Hemodynamics physiology
Hypoxia physiopathology
Neurons physiology
Paraventricular Hypothalamic Nucleus physiology
Respiratory Mechanics physiology
Subjects
Details
- Language :
- English
- ISSN :
- 1522-1490
- Volume :
- 309
- Issue :
- 7
- Database :
- MEDLINE
- Journal :
- American journal of physiology. Regulatory, integrative and comparative physiology
- Publication Type :
- Academic Journal
- Accession number :
- 26157062
- Full Text :
- https://doi.org/10.1152/ajpregu.00540.2014