CHOLINE-ACETYLTRANSFERASE ACTIVITY OF RAT SYNAPTOSOMES IS SENSITIVE TO ENFLURANE, BUT NOT HALOTHANE OR ISOFLURANE

We have examined the activity of choline acetyl transferase (ChAT) in rat cortical synaptosomes in the presence of three volatile anaestheti c agents. enflurane, halothane and isoflurane. The Michaelis constant K-m, for choline was reduced significantly (P = 0.012) in the presence of 6.5% enflurane (3 rat MAC) compared with control samples exposed t o carrier air only, while maximum reaction velocity (Vmax) remained un altered. The reduction in K, was also significant at enflurane concent rations of 4.4% (2 rat MAC) (P = 0.043) and 2.2% (1 rat MAC) (P = 0.04 3). Halothane 3% (2.5 rat MAC) and 4.5% isoflurane (3 rat MAC) had no effect on either kinetic property. if present in vivo, an enflurane-in duced alteration in acetylcholine metabolism, through modified ChAT, m ay contribute to the convulsive properties of this anaesthetic.