ENHANCED CHOLINE-ACETYLTRANSFERASE ACTIVITY DOES NOT EXPLAIN THE ACTION OF INHALED CONVULSANTS

Enhancement of choline acetyltransferase (ChAT) activity and increased intraneuronal acetylcholine (ACh) may explain the convulsant activity of some inhaled compounds. Enflurane, for example, enhances such acti vity. Accordingly, we measured choline acetyltransferase (ChAT) activi ty in rat cortical synaptosomes in the presence of two inhaled convuls ants, flurothyl (CF3CH2OCH2CF3) and 1,2-dichlorohexafluorocyclobutane at partial pressures below and greatly exceeding those which produce c onvulsions in vivo. Neither agent changed the kinetic parameters, maxi mum velocity (vmax) or Michaelis constant (K-m). The vmax for controls in the flurothyl series was 016 (0.06) nmol mg(-1) min(-1) and the K- m was 0.23 (0.11) mmol litre(-1). For the 1,2-dichlorohexafluorocyclob utane series of experiments the results for the controls were vmax 0.2 3 (0.10) nmol mg(-1) min(-1) and K-m 0.20 (0.08) mmol litre(-1). Modif ication of ChAT activity did not contribute to the excitatory effects of these agents.