Fluidization of brain membranes by A2C does not produce anesthesia and does not augment muscimol-stimulated 36Cl- influx.
Intravenous administration of 2-[2-methoxyethoxy]-ethyl 8-[cis-2-n-octylcyclopropyl]-octanoate (A2C) was found to disorder brain membranes but did not produce intoxication or anesthesia in mice. The abilities of A2C and an anesthetic (benzyl alcohol) to inhibit [35S]t-butylbicyclophosphorothionate (TBPS) binding, and modify gamma-aminobutyric acid (GABA) receptor-mediated 36Cl- influx into brain vesicles were then compared. Both of the perturbants inhibited [35S]TBPS binding at the same concentrations at which they reduced membrane order; however, the anesthetic was nearly 4 times more effective in reducing [35S]TBPS binding than was A2C. Muscimol-stimulated 36Cl- uptake was enhanced by benzyl alcohol at a concentration which produced little or no change in membrane order. Concentrations of both A2C and benzyl alcohol which reduced membrane order inhibited muscimol-stimulated 36Cl- influx. Similarly, membrane order and muscimol-activated 36Cl- uptake were reduced in brain vesicles prepared from mice which had received A2C in vivo. The effects of anesthetics on the GABAA receptor-chloride channel complex were analyzed by a two site model of action in which a 'perturbant' site is responsible for decreased 36Cl- uptake; but a distinct 'anesthetic' site is responsible for augmentation of chloride flux and anesthesia.
Buck
K J
KJ
Veterans Administration Medical Center, Denver, CO.
Allan
A M
AM
Harris
R A
RA
D000758:Anesthesia; D000818:Animals; D001592:Benzyl Alcohols / Q000494:pharmacology; D001923:Brain Chemistry / Q000187:drug effects*; D001643:Bridged Bicyclo Compounds / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002712:Chlorides / Q000378:metabolism*; D002713:Chlorine; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008813:Mice, Inbred ICR; D009118:Muscimol / Q000494:pharmacology*; D011868:Radioisotopes; D013228:Stearates / Q000494:pharmacology*; D013229:Stearic Acids / Q000494:pharmacology*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism; D013696:Temperature; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D001592:Benzyl Alcohols; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002712:Chlorides; D011868:Radioisotopes; D013228:Stearates; D013229:Stearic Acids; D009118:Muscimol; D002713:Chlorine; C023714:A(2)C; D005680:gamma-Aminobutyric Acid; C037476:tert-butylbicyclophosphorothionate