Halothane, enflurane, and isoflurane depress the peripheral vagal motor pathway in isolated canine tracheal smooth muscle

J. F. Brichant, Susan Gunst, D. O. Warner, K. Rehder

Research output: Contribution to journalArticle

53 Citations (Scopus)

Abstract

Volatile anesthetics are potent bronchodilators, but the site of action for the dilation is unclear. To determine the site of action of halothane, enflurane, and isoflurane on the peripheral vagal motor pathway, isolated strips of canine trachealis muscle were stimulated before and during exposure to halothane at 0.3, 1.0, 1.7, or 2.4 MAC, enflurane at 1 MAC, or isoflurane at 1 MAC. The sites and methods of stimulation were: 1) postsynaptic nicotinic cholinergic receptors in the intramural parasympathetic ganglia, with 1,1-dimethyl-4-phenyl-piperazinium iodide (DMPP); 2) postganglionic cholinergic nerve fibers, with electrical field stimulation (EFS); and 3) muscarinic cholinergic receptors of the smooth muscle, with acetylcholine (ACh). The concentration-response curve to DMPP was significantly shifted to the right by 0.3 MAC halothane, whereas 0.3 MAC halothane had no significant effect on the concentration-response curves to ACh and EFS. At concentrations >1 MAC of halothane, enflurane, or isoflurane, concentration-response curves to all three stimuli were shifted significantly to the right; i.e., the contractile responses to ACh, EFS, and DMPP were reduced. At all concentrations of halothane the force of contraction was significantly more reduced during stimulation with DMPP than during stimulation with ACh, and at halothane concentrations ≥1.7 MAC the response to EFS was significantly more reduced than that to ACh. We conclude that halothane, enflurane, and isoflurane attenuated airway constriction by several mechanisms, including 1) reduced excitability of the post-synaptic nicotinic receptors of the intramural parasympathetic ganglia and 2) an effect on the smooth muscle and/or on the muscarinic receptors. At higher concentrations of halothane (≥1.7 MAC), post-ganglionic nerve function was also affected.

Original languageEnglish (US)
Pages (from-to)325-332
Number of pages8
JournalAnesthesiology
Volume74
Issue number2
StatePublished - 1991
Externally publishedYes

Fingerprint

Efferent Pathways
Enflurane
Isoflurane
Halothane
Smooth Muscle
Canidae
Dimethylphenylpiperazinium Iodide
Acetylcholine
Electric Stimulation
Parasympathetic Ganglia
Nicotinic Receptors
Cholinergic Receptors
Muscarinic Receptors
Cholinergic Fibers
Neurotransmitter Receptor
Bronchodilator Agents
Nerve Fibers
Constriction
Anesthetics
Dilatation

Keywords

  • Anesthetics, volatile: halothane; enflurane; isoflurane
  • Nerve, vagus: smooth muscle contraction
  • Parasympathetic nervous system: acetylcholine; intramural parasympathetic ganglia; electrical field stimulation; postganglionic fiber

ASJC Scopus subject areas

  • Anesthesiology and Pain Medicine

Cite this

Halothane, enflurane, and isoflurane depress the peripheral vagal motor pathway in isolated canine tracheal smooth muscle. / Brichant, J. F.; Gunst, Susan; Warner, D. O.; Rehder, K.

In: Anesthesiology, Vol. 74, No. 2, 1991, p. 325-332.

Research output: Contribution to journalArticle

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