Kobayashi Katsunori, Ikeda Yumiko, Suzuki Hidenori
Department of Pharmacology, Nippon Medical School, 1-1-5 Sendagi, Bunkyo-ku, Tokyo 113-8602, Japan.
Eur J Neurosci. 2006 Oct;24(7):1867-73. doi: 10.1111/j.1460-9568.2006.05079.x. Epub 2006 Oct 16.
The hippocampus has long been implicated in memory formation. Although accumulating evidence suggests involvement of the hippocampus in other brain functions including locomotor regulation and emotional processes, cellular and synaptic bases underlying these functions remain largely unknown. We here report that environmental manipulations in mice unveiled the association of locomotor activity with the hippocampal mossy fibre (MF) synaptic transmission. Electrophysiological recordings of synaptic responses were made using hippocampal slices prepared from mice whose behaviour had been analysed. Environmental enrichment induced parallel decreases in open-field locomotor activity and MF synaptic facilitation. Facilitation induced by paired-pulse stimulation at relatively long intervals (>or=200 ms) was selectively reduced while the basal synaptic efficacy and high-frequency transmission were unaffected. Social isolation caused a change in behaviour in an elevated plus-maze, but neither the open-field activity nor the MF synaptic transmission was significantly altered. Effects of dopamine, a neurotransmitter essential for locomotor regulation, on the MF synapse were also examined using these mice. Environmental manipulations did not cause significant changes in potentiation of the MF synaptic transmission induced by dopamine. However, analysis of behavioural and electrophysiological results in individual subjects revealed that locomotor activity negatively correlates with magnitude of the dopamine-induced potentiation. These results suggest that the MF synapse plays important roles in the regulation of locomotor activity. We propose that the MF synapse can serve as the synaptic model for certain forms of locomotor regulation, with potential importance for investigation of the pathophysiology of psychiatric diseases using animal models.
海马体长期以来一直被认为与记忆形成有关。尽管越来越多的证据表明海马体参与了包括运动调节和情绪过程在内的其他脑功能，但这些功能背后的细胞和突触基础在很大程度上仍然未知。我们在此报告，对小鼠的环境操控揭示了运动活动与海马体苔藓纤维（MF）突触传递之间的关联。使用从行为已被分析的小鼠制备的海马体切片进行突触反应的电生理记录。环境丰富化导致旷场运动活动和MF突触易化平行下降。在相对较长间隔（≥200毫秒）下由双脉冲刺激诱导的易化被选择性降低，而基础突触效能和高频传递不受影响。社会隔离导致高架十字迷宫中的行为发生变化，但旷场活动和MF突触传递均未显著改变。还使用这些小鼠研究了多巴胺（一种对运动调节至关重要的神经递质）对MF突触的影响。环境操控并未导致多巴胺诱导的MF突触传递增强发生显著变化。然而，对个体受试者的行为和电生理结果分析表明，运动活动与多巴胺诱导的增强幅度呈负相关。这些结果表明MF突触在运动活动调节中起重要作用。我们提出MF突触可作为某些形式运动调节的突触模型，对使用动物模型研究精神疾病的病理生理学具有潜在重要性。
