title: Modification of central nervous system effects of laudanosine by inhalation anaesthetics.
abstract: To determine the effect of inhalation anaesthetics on the plasma concentration of laudanosine necessary to produce CNS excitation, we administered laudanosine 0.5 mg kg-1 min-1 i.v. to 40 rabbits under eight study conditions: 1.0 or 0.7% halothane, 1.6% isoflurane, 2.0% enflurane, during normocapnia and hypocapnia; 70% nitrous oxide, alone and with 1.0% halothane, and room air (control). At the onset of purposeless, unco-ordinated movements of the entire body, blood samples were obtained to determine the CNS excitation-threshold plasma concentration (ETPC) of laudanosine. During normocapnia, 1.0% halothane, 1.6% isoflurane and 2.0% enflurane increased ETPC (mean (SD) 11.8 (2.5), 11.3 (2.8) and 9.1 (1.4) micrograms ml-1, respectively) from control (5.0 (0.9) microgram ml-1). ETPC during enflurane anaesthesia did not change significantly with hypocapnia. Nitrous oxide, alone or in combination with halothane, did not change ETPC. The combination of nitrous oxide with 1.0% halothane significantly decreased ETPC to less than that for halothane alone (6.7 (1.2) v. 11.8 (2.5) micrograms ml-1, respectively).
authors.affiliation: Department of Anesthesia, University of California, San Francisco.
authors.forename: W Z
authors.initials: WZ
authors.lastname: Shi
authors.forename: M R
authors.initials: MR
authors.lastname: Fahey
authors.forename: D M
authors.initials: DM
authors.lastname: Fisher
authors.forename: R D
authors.initials: RD
authors.lastname: Miller
mesh_terms: D000769:Anesthesia, Inhalation; D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D001921:Brain / Q000187:drug effects*; D004347:Drug Interactions; D007546:Isoquinolines / Q000097:blood / Q000494:pharmacology*; D008297:Male; D011817:Rabbits; D012684:Sensory Thresholds / Q000187:drug effects
chemical_list: D000777:Anesthetics; D007546:Isoquinolines; C001522:laudanosine