Choline acetyltransferase activity of rat synaptosomes is sensitive to enflurane, but not halothane or isoflurane.
We have examined the activity of choline acetyltransferase (ChAT) in rat cortical synaptosomes in the presence of three volatile anaesthetic agents: enflurane, halothane and isoflurane. The Michaelis constant Km, for choline was reduced significantly (P = 0.012) in the presence of 6.5% enflurane (3 rat MAC) compared with control samples exposed to carrier air only, while maximum reaction velocity (Vmax) remained unaltered. The reduction in Km was also significant at enflurane concentrations of 4.4% (2 rat MAC) (P =  0.043) and 2.2% (1 rat MAC) (P = 0.043). 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-induced alteration in acetylcholine metabolism, through modified ChAT, may contribute to the convulsive properties of this anaesthetic.
Griffiths
R
R
Department of Anaesthesia, University of Leicester, Leicester Royal Infirmary.
Boyle
E
E
Greiff
J M
JM
Rowbotham
D J
DJ
Norman
R I
RI
D000777:Anesthetics / Q000494:pharmacology*; D000818:Animals; D002795:Choline O-Acetyltransferase / Q000378:metabolism*; D004737:Enflurane / Q000494:pharmacology; D005260:Female; D006221:Halothane / Q000494:pharmacology; D066298:In Vitro Techniques; D007530:Isoflurane / Q000494:pharmacology; D007700:Kinetics; D010313:Partial Pressure; D051381:Rats; D017208:Rats, Wistar; D013574:Synaptosomes / Q000187:drug effects* / Q000201:enzymology
D000777:Anesthetics; D004737:Enflurane; D007530:Isoflurane; D002795:Choline O-Acetyltransferase; D006221:Halothane