Modulation of the sympathetic response to acute hypoxia by the caudal ventrolateral medulla in rats
| Autor: | Daniel A, Mandel, Ann M, Schreihofer |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2008 |
| Předmět: |
Male
Sympathetic Nervous System Models Neurological Glutamic Acid Blood Pressure Vagotomy Bicuculline Kynurenic Acid Rats Sprague-Dawley Cardiovascular Physiological Phenomena Receptors Glycine Sodium Cyanide Integrative Animals GABA-A Receptor Antagonists Hypoxia GABA Agonists Respiratory Burst Neurons Medulla Oblongata Muscimol Splanchnic Nerves Strychnine Rats Phrenic Nerve Pyridazines Respiratory Mechanics Respiratory Physiological Phenomena Excitatory Amino Acid Antagonists Perspectives |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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