Effect of Ketamine Anaesthesia on the Content of Monoamines and their Metabolites in the Rat Brain

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Abstract
The effects of ketamine anaesthesia (100 mg/kg i.p.) on the content of brain 5‐hydroxytryptamine (5HT), 5‐hydroxyindoleacetic acid (5HIAA), noradrenaline (NA), dopamine (DA) and homovanillic acid (HVA) were studied in male Wistar rats.Fifteen min after ketamine injection, when the rats were deeply anaesthetized, the 5HT content in many brain regions tended to be increased. An opposite tendency was found in the brain 5HIAA content. In rats treated with probenecid, which markedly lengthened ketamine anaesthesia, the accumulation of SHIAA was significantly reduced by ketamine. In addition to ketamine anaesthesia, probenecid was found to lengthen thiopental anaesthesia. One hour after the ketamine administration, when the rats were no longer anaesthetized but were excited, the brain NA concentration was increased by 17% (P< 0.02). The brain DA content was unchanged, but at 15 min and 1 hour after ketamine administration the striatal HVA content was increased by about 55% (P< 0.05), suggesting an increased turnover of DA.The results suggest that during recovery from ketamine anaesthesia the increased NA content and the increased DA turnover may be associated with the post‐anaesthetic excitement of the rat, whereas the decrease in brain 5HIAA content may coincide with the deepening of ketamine anaesthesia.