Spinal AMP kinase activity differentially regulates phrenic motor plasticity

Raphael Rodrigues Perim, Daryl P. Fields, Gordon S. Mitchell

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Acute intermittent hypoxia (AIH) elicits phrenic motor plasticity via multiple distinct cellular mechanisms. With moderate AIH, phrenic motor facilitation (pMF) requires Gq proteincoupled serotonin type 2 receptor activation, ERK MAP kinase activity, and new synthesis of brain-derived neurotrophic factor. In contrast, severe AIH elicits pMF by an adenosine-dependent mechanism that requires exchange protein activated by cAMP, Akt, and mammalian target of rapamycin (mTOR) activity, followed by new tyrosine receptor kinase B protein synthesis; this same pathway is also initiated by Gs protein-coupled serotonin 7 receptors (5-HT7). Because the metabolic sensor AMP-activated protein kinase (AMPK) inhibits mTOR-dependent protein synthesis, and mTOR signaling is necessary for 5-HT7 but not 5-HT2 receptor-induced pMF, we hypothesized that spinal AMPK activity differentially regulates pMF elicited by these distinct receptor subtypes. Serotonin type 2A receptor [5-HT2A; (±)-2,5-dimethoxy-4-iodoamphetamine hydrochloride] or 5-HT7 (AS-19) receptor agonists were administered intrathecally at C4 (3 injections, 5-min intervals) while recording integrated phrenic nerve activity in anesthetized, vagotomized, paralyzed, and ventilated rats. Consistent with our hypothesis, spinal AMPK activation with 2-deoxyglucose or metformin blocked 5-HT7, but not 5-HT2A receptor- induced pMF; in both cases, pMF inhibition was reversed by spinal administration of the AMPK inhibitor compound C. Thus, AMPK differentially regulates cellular mechanisms of serotonininduced phrenic motor plasticity. NEW & NOTEWORTHY Spinal AMP-activated protein kinase (AMPK) overactivity, induced by local 2-deoxyglucose or metformin administration, constrains serotonin 7 (5-HT7) receptor-induced (but not serotonin type 2A receptor-induced) respiratory motor facilitation, indicating that metabolic challenges might regulate specific forms of respiratory motor plasticity. Pharmacological blockade of spinal AMPK activity restores 5-HT7 receptor-induced respiratory motor facilitation in the presence of either 2-deoxyglucose or metformin, showing that AMPK is an important regulator of 5-HT7 receptorinduced respiratory motor plasticity.

Original languageEnglish (US)
Pages (from-to)523-533
Number of pages11
JournalJournal of applied physiology
Volume128
Issue number3
DOIs
StatePublished - 2020
Externally publishedYes

Keywords

  • AMPK
  • Phrenic motor plasticity
  • Serotonin receptors

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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