Influence of anaesthetics on rat striatal dopamine metabolism in vivo

The effects of 4 anaesthetics, halothane, alpha-chloralose, chloral hydrate and pentobarbitone, on rat striatal extracellular dihydroxyphenylacetic acid (DOPAC) levels were determined using in vivo voltammetry. Stable baseline levels of DOPAC were maintained under halothane/N2O and alpha-chloralose while the extracellular levels of DOPAC gradually declined under chloral hydrate or pentobarbitone anaesthesia. Administration of haloperidol (0.3 mg/kg i.p.) significantly increased DOPAC using halothane/N2O, alpha-chloralose or chloral hydrate but not under pentobarbitone anaesthesia. The greatest increase in DOPAC was seen in rats anaesthetized with alpha-chloralose greater than halothane/N2O greater than chloral hydrate greater than pentobarbitone. Apomorphine (0.5 mg/kg s.c.) given 2 h after haloperidol partially reversed the increase in DOPAC produced by haloperidol. The results suggest care needs to be exercised in the choice of anaesthetic used for voltammetric studies with pentobarbitone being the least recommended.