BJA Advance Access originally published online on January 22, 2004
British Journal of Anaesthesia, 2004, Vol. 92, No. 3 424-426
© 2004 The Board of Management and Trustees of the British Journal of Anaesthesia
Short Communications |
Opposite effects of depressant and convulsant barbiturate stereoisomers on acetylcholine release from the rat hippocampus in vivo
Department of Anesthesiology, Yokohama City University School of Medicine, 3-9 Fukuura, Kanasawa-Ku, Yokohama 236-0004, Japan
*Corresponding author. E-mail: inagawa@med.yokohama-cu.ac.jp
Background. It has been shown that the R() isomer of 1-methyl-5-phenyl-5-propyl barbituric acid (MPPB) induces loss of the righting reflex (LRR), while S(+)-MPPB causes pure excitatory effects, including convulsions, in vivo.
Methods. We studied the effects of the depressant and convulsant MPPB stereoisomers on rat hippocampal acetylcholine (ACh) release in vivo, using a brain microdialysis technique in freely moving animals.
Results. R()-MPPB 60 and 90 mg kg1 i.p. decreased ACh release from the rat hippocampus by 44.1 (8.2)% and 60.8 (8.2)%, respectively. In the hippocampus, the local application of bicuculline, a
-aminobutyric acid (GABA)A receptor antagonist, 1 µmol litre1 antagonized the inhibitory effects of R()-MPPB 90 mg kg1 i.p. In contrast, R()-MPPB, S(+)-MPPB 60 and 90 mg kg1 i.p. increased ACh release to 151.8 (6.8)% and 169.6 (11.1)% of the basal release, respectively.
Conclusions. Our results demonstrated that R()-MPPB decreased, while S(+)-MPPB increased, rat hippocampal ACh release and that the inhibitory effects of R()-MPPB may involve the GABAA receptor in vivo. These data imply that changes in hippocampal ACh due to these agents may be related to their central inhibitory and stimulatory actions in vivo.
Br J Anaesth 2004; 92: 4246