Modulation of the sympathetic response to acute hypoxia by the caudal ventrolateral medulla in rats.

Article date: 2008/12/3

PubMed ID: 2231403

Journal name: The Journal of physiology (ISSN: 1469-7793)

DOI: 10.1113/jphysiol.2008.161760


Hypoxia elevates splanchnic sympathetic nerve activity (SNA) with differential effects during inspiration and expiration by unresolved central mechanisms. We examined the hypothesis that cardiovascular-related neurones in the caudal ventrolateral medulla (CVLM) contribute to the complex sympathetic response to hypoxia. In chloralose-anaesthetized, ventilated, vagotomized rats, acute hypoxia (10% O2, 60 s) evoked an increase in SNA (103 +/- 12%) that was characterized by a decrease in activity during early inspiration followed by a prominent rise during expiration. Some recorded baro-activated CVLM neurones (n = 13) were activated by hypoxia, and most of these neurones displayed peak activity during inspiration that was enhanced during hypoxia. In contrast, other baro-activated CVLM neurones were inhibited during hypoxia (n = 6), and most of these neurones showed peak activity during expiration prior to the onset of hypoxia. Microinjection of the glutamate antagonist kynurenate into the CVLM eliminated the respiratory-related fluctuations in SNA during hypoxia and exaggerated the magnitude of the sympathetic response. In contrast, microinjection of a GABA(A) antagonist (bicuculline or gabazine) into the CVLM dramatically attenuated the sympathetic response to hypoxia. These data suggest the response to hypoxia in baro-activated CVLM neurones is related to their basal pattern of respiratory-related activity, and changes in the activity of these neurones is consistent with a contribution to the respiratory-related sympathetic responses to hypoxia. Furthermore, both glutamate and GABA in the CVLM contribute to the complex sympathetic response to acute hypoxia.

Author List: Mandel Daniel A, Schreihofer Ann M

Publication Types: Journal Article

Article Date: 2008/12/01

Substances mentioned in the article: Excitatory Amino Acid Antagonists; GABA Agonists; GABA-A Receptor Antagonists; Pyridazines; Receptors, Glycine; Muscimol; Glutamic Acid; gabazine; Kynurenic Acid; Strychnine; Sodium Cyanide; Bicuculline;

Mesh terms: Animals; Bicuculline/pharmacology; Blood Pressure/drug effects; Excitatory Amino Acid Antagonists/pharmacology; GABA Agonists/pharmacology; GABA-A Receptor Antagonists; Glutamic Acid/pharmacology; Hypoxia/physiopathology; Kynurenic Acid/pharmacology; Male; Medulla Oblongata/cytology; Models, Neurological; Muscimol/pharmacology; Neurons/drug effects; Phrenic Nerve/drug effects; Pyridazines/pharmacology; Rats; Rats, Sprague-Dawley; Receptors, Glycine/antagonists & inhibitors; Respiratory Mechanics/drug effects; Sodium Cyanide/pharmacology; Splanchnic Nerves/drug effects; Strychnine/pharmacology; Sympathetic Nervous System/cytology; Vagotomy;

Citations: - 19147671

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