Faculty Collaboration Database

Sevoflurane depresses glutamatergic neurotransmission to brainstem inspiratory premotor neurons but not postsynaptic receptor function in a decerebrate dog model. Anesthesiology 2005 Jul;103(1):50-6

Date

06/29/2005

Pubmed ID

15983456

DOI

10.1097/00000542-200507000-00011

Scopus ID

2-s2.0-21744446111 (requires institutional sign-in at Scopus site)   17 Citations

Abstract

BACKGROUND: Inspiratory bulbospinal neurons in the caudal ventral medulla are premotor neurons that drive motoneurons, which innervate pump muscles such as the diaphragm and external intercostals. Excitatory drive to these neurons is mediated by N-methyl-d-aspartate (NMDA) receptors and alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptors and is modulated by an inhibitory gamma-aminobutyric acid type A (GABAA)ergic input. The authors investigated the effect of sevoflurane on these synaptic mechanisms in decerebrate dogs.

METHODS: Studies were performed in decerebrate, vagotomized, paralyzed, and mechanically ventilated dogs during hypercapnic hyperoxia. The effect of 1 minimum alveolar concentration sevoflurane on extracellularly recorded activity of single neurons was measured during localized picoejection of the GABAA receptor blocker bicuculline and the glutamate agonists AMPA and NMDA. Complete blockade of the GABAAergic mechanism by bicuculline allowed differentiation between the effects of sevoflurane on overall GABAAergic inhibition and on overall glutamatergic excitation. The neuronal responses to exogenous AMPA and NMDA were used to estimate the anesthetic effect on postsynaptic glutamatergic neurotransmission.

RESULTS: One minimum alveolar concentration sevoflurane depressed the spontaneous activity of 23 inspiratory premotor neurons by (mean +/- SD) 30.0 +/- 21.0% (P < 0.001). Overall glutamatergic excitation was depressed 19.2 +/- 18.5% (P < 0.001), whereas overall GABAAergic inhibition was enhanced by 11.9 +/- 25.1% (P < 0.05). The postsynaptic responses to exogenous AMPA and NMDA did not change.

CONCLUSION: One minimum alveolar concentration depressed the activity of inspiratory premotor neurons by a reduction of glutamatergic excitation and an increase in overall inhibition. The postsynaptic AMPA and NMDA receptor response was unchanged. These findings contrast with studies in inspiratory premotor neurons where halothane did not change overall inhibition but significantly reduced the postsynaptic glutamate receptor response.

Author List

Stucke AG, Zuperku EJ, Tonkovic-Capin V, Krolo M, Hopp FA, Kampine JP, Stuth EA

Authors

Astrid G. Stucke MD Professor in the Anesthesiology department at Medical College of Wisconsin
Eckehard A. Stuth MD Professor in the Anesthesiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Animals
Brain Stem
Decerebrate State
Dogs
Dose-Response Relationship, Drug
Inhalation
Methyl Ethers
Motor Neurons
N-Methylaspartate
Neurons
Receptors, Glutamate
Synapses
Synaptic Transmission