Fachbereich Veterinärmedizin



    Anxiety but not arousal increases 5-HT release in rat hippocampus (2005)

    Rex, A.
    Voigt, J. P.
    Fink, H.
    8th World Congress of Biological Psychiatry
    Wien/Österreich, 28.06. – 03.07.2005
    The World Journal of Biological Psychiatry; Vol. 6(Suppl. 1) — S. 334–335
    ISSN: 1562-2975
    Institut für Pharmakologie und Toxikologie

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    Abstract / Zusammenfassung

    Anxiety but not arousal increases 5-HT release in rat hippocampus

    Objectives: The central serotonergic system is involved in the aetiology of numerous disease states, including depression and anxiety disorders. Drugs that alter serotonin (5-HT) function are the frontline treatment of anxiety disorders. Several studies have shown that exposure of rats to animal tests for anxiety increases extracellular 5-HT in the cortex or the hippocampus.
    Aim of the study is to discriminate whether the increase in extracellular 5-HT is caused by aversive conditions of an animal test for anxiety or by an unconditioned stressor evoking arousal.
    Methods: The present study investi¬gates the effects of exposure to an acoustic stimulus (95 dB) or to the ele¬vated plus maze (X-maze, illumination: 210 lux open arms, 160 lux closed arms) or to a X-maze with closed arms only (C-maze), for 20 minutes respectively, on 5-HT relea¬se in the ventral hippocampus of rats, determined by in vivo microdialysis followed by HPLC and electrochemical detection.
    Results: Exposure of male Fischer 344 rats (Charles River, Germany, 220±30 g) to the X-maze induced an ‘anxious’ behaviour and increased extracellular 5 HT to 165% of basal release. However, exposure to white noise in the familiar surroundings of the home cage did not change extracellular 5-HT in the hippocampus, even though locomotor activity and the percentage of animals digging in the bedding were increased.
    Conclusions: The increased 5-HT release concurred with exposure to the X maze but not to the less aversive but new surroundings of the C-maze with or exposure to white noise. This indicates a strong relationship between 5-HT release and behaviour indicative of "anxiety". Our results are backed up by recent studies showing ‘anxiolytic’ effects of Neuropeptide S accompanied by increased motor activity. It is suggested that the relationship between arousal/non-specific behavioural activation and 5-HT in general is not necessarily linked in the rat hippocampus.