Effects of volatile anesthetics on vagal C-fiber activities and their reflexes in anesthetized dogs.
Effects of halothane, enflurane, isoflurane, and sevoflurane on vagal capsaicin (CAPS)-sensitive C-fibers were elucidated in anesthetized dogs. The CAPS-sensitive C-fibers were significantly stimulated by all volatile anesthetics with a significantly greater response to halothane than with sevoflurane. A significant increase in respiratory frequency (fR) and a significant decrease in tidal volume (VT) were observed with halothane and isoflurane, and a significant increase in fR was observed with sevoflurane. In contrast, a significant decrease in fR was induced by enflurane. The tachypnea induced by halothane, isoflurane, and sevoflurane was significantly reduced or no longer observed after perineural CAPS-treatment or bilateral vagotomy, whereas the slowing of respiration observed with enflurane was not affected by either of these treatments. These results suggest that vagal C-fibers play an important role in the reflex tachypnea that occurs with halothane, isoflurane, and sevoflurane.
Mutoh
T
T
Division of Veterinary Medical Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan. tmutoh@ucdavis.edu
Tsubone
H
H
Nishimura
R
R
Sasaki
N
N
D000758:Anesthesia; D018685:Anesthetics, Inhalation / Q000633:toxicity*; D000818:Animals; D002211:Capsaicin / Q000494:pharmacology; D004285:Dogs; D005260:Female; D006221:Halothane / Q000633:toxicity; D007530:Isoflurane / Q000633:toxicity; D008297:Male; D008738:Methyl Ethers / Q000633:toxicity; D009412:Nerve Fibers / Q000187:drug effects*; D009475:Neurons, Afferent / Q000187:drug effects; D012018:Reflex / Q000187:drug effects*; D015656:Respiratory Mechanics / Q000187:drug effects; D000077149:Sevoflurane; D014628:Vagotomy; D014630:Vagus Nerve / Q000166:cytology* / Q000187:drug effects
D018685:Anesthetics, Inhalation; D008738:Methyl Ethers; D000077149:Sevoflurane; D007530:Isoflurane; D002211:Capsaicin; D006221:Halothane