Cross-talk inhibition between 5-HT2B and 5-HT7 receptors in phrenic motor facilitation via NADPH oxidase and PKA

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

Research output: Contribution to journalArticlepeer-review

19 Scopus citations

Abstract

Intermittent spinal serotonin receptor activation elicits phrenic motor facilitation (pMF), a form of spinal respiratory motor plasticity. Episodic activation of either serotonin type 2 (5-HT2) or type 7 (5-HT7) receptors elicits pMF, although they do so via distinct cellular mechanisms known as the Q (5-HT2) and S (5-HT7) pathways to pMF. When coactivated, these pathways interact via mutual cross-talk inhibition. Although we have a rudimentary understanding of mechanisms mediating cross-talk interactions between spinal 5-HT2subtype A (5-HT2A) and 5-HT7receptor activation, we do not know if similar interactions exist between 5-HT2subtype B (5-HT2B) and 5-HT7receptors. We confirmed that either spinal 5-HT2Bor 5-HT7receptor activation alone elicits pMF and tested the hypotheses that 1) concurrent activation of both receptors suppresses pMF due to cross-talk inhibition; 2) 5-HT7receptor inhibition of 5-HT2Breceptor-induced pMF requires protein kinase A (PKA) activity; and 3) 5-HT2Breceptor inhibition of 5-HT7receptorinduced pMF requires NADPH oxidase (NOX) activity. Selective 5-HT2Band 5-HT7receptor agonists were administered intrathecally at C4 (3 injections, 5-min intervals) to anesthetized, paralyzed, and ventilated rats. Whereas integrated phrenic nerve burst amplitude increased after selective spinal 5-HT2Bor 5-HT7receptor activation alone (i.e., pMF), pMF was no longer observed with concurrent 5-HT2Band 5-HT7receptor agonist administration. With concurrent receptor activation, pMF was rescued by inhibiting either NOX or PKA activity, demonstrating their roles in cross-talk inhibition between these pathways to pMF. This report demonstrates cross-talk inhibition between 5-HT2B- and 5-HT7receptor-induced pMF and that NOX and PKA activity are necessary for that cross-talk inhibition.

Original languageEnglish (US)
Pages (from-to)R709-R715
JournalAmerican Journal of Physiology - Regulatory Integrative and Comparative Physiology
Volume314
Issue number5
DOIs
StatePublished - May 2018
Externally publishedYes

Keywords

  • Intermittent hypoxia
  • Long-term facilitation
  • NADPH oxidase
  • Protein kinase A
  • Respiratory plasticity

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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