Linthorst Astrid C E, Flachskamm Cornelia, Reul Johannes M H M
Section of Neurochemistry, Max Planck Institute of Psychiatry, Munich, Germany.
Stress. 2008 Mar;11(2):88-100. doi: 10.1080/10253890701533231.
Forced swimming is a behavioural stress model increasingly used to investigate the neurocircuitry of stress responses. Although forced swim stress clearly is a psychological stressor (anxiety, panic), its physical aspects are often neglected. There are indications that behavioural and neurochemical responses to swim stress depend on the water temperature. Thus, we investigated the responsiveness of hippocampal serotonergic neurotransmission (important in the coordination of stress responses), and of behaviour and core body temperature to forced swimming at different water temperatures (19, 25 and 35 degrees C). In vivo microdialysis and biotelemetry in freely-behaving rats were used. Dialysates were analysed for serotonin (5-HT) and its metabolite 5-HIAA (5-hydroxyindoleacetic acid) by HPLC with electrochemical detection. Forced swimming in water at 25 and 19 degrees C decreased core body temperature by 8 and 12 degrees C, respectively. A rapid and pronounced increase in hippocampal 5-HT and 5-HIAA was found in rats that swam at 35 degrees C, whereas biphasic responses in 5-HT and 5-HIAA were observed at 25 and 19 degrees C. Also swim stress behaviour and post-stress home cage behaviour depended on the water temperature. Comparing the serotonergic and core body temperature changes revealed that a combination of two different 5-HT and 5-HIAA responses seems to shape the neurotransmitter response. Swimming-induced increases in hippocampal extracellular concentrations of 5-HT and 5-HIAA occurred at all water temperatures, but these increases were temporarily quenched, or concentrations were transistently decreased, when core body temperature fell below 31 degrees C in water at 25 or 19 degrees C. These data demonstrate that water temperature is a key factor determining the impact of forced swim stress on behaviour and neurochemistry, and underscore that changes in these parameters should be interpreted in the light of the autonomic responses induced by this stressor.
强迫游泳是一种越来越多地用于研究应激反应神经回路的行为应激模型。尽管强迫游泳应激显然是一种心理应激源（焦虑、恐慌），但其身体方面常常被忽视。有迹象表明，对游泳应激的行为和神经化学反应取决于水温。因此，我们研究了海马5-羟色胺能神经传递（在应激反应协调中起重要作用）以及行为和核心体温对不同水温（19、25和35摄氏度）下强迫游泳的反应。使用了自由活动大鼠的体内微透析和生物遥测技术。通过具有电化学检测的高效液相色谱法分析透析液中的5-羟色胺（5-HT）及其代谢物5-羟吲哚乙酸（5-HIAA）。在25摄氏度和19摄氏度的水中强迫游泳分别使核心体温降低了8摄氏度和12摄氏度。在35摄氏度游泳的大鼠中发现海马5-HT和5-HIAA迅速且显著增加，而在25摄氏度和19摄氏度时观察到5-HT和5-HIAA的双相反应。游泳应激行为和应激后在饲养笼中的行为也取决于水温。比较5-羟色胺能和核心体温变化发现，两种不同的5-HT和5-HIAA反应的组合似乎决定了神经递质反应。在所有水温下，游泳均会导致海马细胞外5-HT和5-HIAA浓度增加，但当在25摄氏度或19摄氏度的水中核心体温降至31摄氏度以下时，这些增加会暂时被抑制，或者浓度会短暂降低。这些数据表明，水温是决定强迫游泳应激对行为和神经化学影响的关键因素，并强调这些参数的变化应根据这种应激源引起的自主反应来解释。
