The effects of anaesthesia and hypothermia on interstitial concentrations of acetylcholine and choline in rat striatum.

The effects of the general anaesthetics pentobarbital, chloral hydrate, and halothane on interstitial concentrations of acetylcholine (ACh) in rat striatum were determined using in vivo microdialysis. All 3 anaesthetics decreased ACh. Emergence from anaesthesia coincided with a recovery of ACh to about 80% of basal values. Pentobarbital increased choline in a profile that was the mirror image of ACh. Chloral hydrate had a biphasic effect on choline, consisting of a shortlasting (20 min) initial decrease followed by an increase. When halothane anaesthetized rats were subjected to forced hypothermia by placing them on ice for 30 min, ACh release was further depressed whereas choline was greatly increased. These finding demonstrate that general anaesthetics decrease extracellular concentrations of ACh in the rat striatum and that this effect can be exacerbated by hypothermia.