Enhanced baroreflex-mediated inhibition of respiration after muscimol dialysis in the rostroventral medulla

J Appl Physiol (1985). 2002 Jun;92(6):2554-64. doi: 10.1152/japplphysiol.00895.2001.

Abstract

The rostral ventral medulla (RVM) may be important in the control of cardiorespiratory interactions. We hypothesized that inhibition of the RVM would enhance inhibition of breathing associated with transient blood pressure elevations. In 25 piglets 3-16 days of age, we studied the effect of acutely increasing blood pressure, by systemic infusion of phenylephrine, on respiratory activity before and after inhibition of neural activity in the RVM by dialysis of 10 mM muscimol, a GABA(A)-receptor agonist. Muscimol dialysis through probes that were placed along the ventral medullary surface from approximately 1 mm rostral to the facial nucleus to approximately 0.5 mm caudal to the facial nucleus augmented the respiratory inhibition associated with acute increases in blood pressure. No similar enhancement of respiratory inhibition after phenylephrine treatment was seen in six control animals that did not receive muscimol dialysis. We conclude that the piglet RVM participates in cardiorespiratory interactions and that dysfunction of homologous regions in the human infant could lead to cardiorespiratory instability and may be involved in the pathogenesis of sudden infant death syndrome.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Animals, Newborn
  • Baroreflex / physiology*
  • Dialysis
  • GABA Agonists / pharmacology*
  • Medulla Oblongata / physiology*
  • Muscimol / pharmacology*
  • Phenylephrine / pharmacology
  • Respiration / drug effects
  • Respiratory Physiological Phenomena*
  • Swine
  • Time Factors
  • Vasoconstrictor Agents / pharmacology

Substances

  • GABA Agonists
  • Vasoconstrictor Agents
  • Phenylephrine
  • Muscimol