Effects of halothane and nitrous oxide anaesthesia on 5-HT turn-over in the rat brain.
The effects of anaesthesia with halothane and nitrous oxide on the turn-over of 5-HT in the rat brain were analysed. The rate of 5-HT synthesis was estimated on the basis of 5-HTP accumulation following 5-HTP decarboxylase inhibition. Inhalation anaesthetics reduced the rate of 5-HT synthesis in the whole brain, this effect being particularly marked in the forebrain. In addition, the reduction of the rate of 5-HT synthesis was still detected after a large tryptophan loading indicating that halothane and nitrous oxide anaesthesia reduced the activity of tryptophan hydroxylase in vivo. The utilization of 5-HT was also delayed during anaesthesia since the rate of 5-HT disappearance following the inhibition of its synthesis at the decarboxylation step was decreased in the whole brain. In spite of this reduced turnover of 5-HT in the brain of rats exposed to inhalation anaesthetics, the 5-HIAA levels were permanently elevated. This was the result of a partial inhibition of the active elimination of the acidic metabolite from the brain during this kind of anaesthesia.
D006916:5-Hydroxytryptophan / Q000378:metabolism; D000758:Anesthesia; D000818:Animals; D001545:Benserazide / Q000494:pharmacology; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D006221:Halothane / Q000494:pharmacology*; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D009609:Nitrous Oxide / Q000494:pharmacology*; D010293:Pargyline / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000096:biosynthesis / Q000378:metabolism*; D013997:Time Factors; D014364:Tryptophan / Q000097:blood / Q000378:metabolism; D014443:Tyrosine / Q000097:blood
D012701:Serotonin; D014443:Tyrosine; D006897:Hydroxyindoleacetic Acid; D001545:Benserazide; D014364:Tryptophan; D010293:Pargyline; D006916:5-Hydroxytryptophan; D009609:Nitrous Oxide; D006221:Halothane