Walker M C, Ruiz A, Kullmann D M
Department of Clinical Neurology, Institute of Neurology, University College London, Queen Square, WC1N 3BG, London, United Kingdom.
Neuron. 2001 Mar;29(3):703-15. doi: 10.1016/s0896-6273(01)00245-8.
Mossy fibers are the sole excitatory projection from dentate gyrus granule cells to the hippocampus, where they release glutamate, dynorphin, and zinc. In addition, mossy fiber terminals show intense immunoreactivity for the inhibitory neurotransmitter GABA. Fast inhibitory transmission at mossy fiber synapses, however, has not previously been reported. Here, we show that electrical or chemical stimuli that recruit dentate granule cells elicit monosynaptic GABA(A) receptor-mediated synaptic signals in CA3 pyramidal neurons. These inhibitory signals satisfy the criteria that distinguish mossy fiber-CA3 synapses: high sensitivity to metabotropic glutamate receptor agonists, facilitation during repetitive stimulation, and NMDA receptor-independent long-term potentiation. GABAergic transmission from the dentate gyrus to CA3 has major implications not only for information flow into the hippocampus but also for developmental and pathological processes involving the hippocampus.
苔藓纤维是从齿状回颗粒细胞到海马体的唯一兴奋性投射，它们在海马体中释放谷氨酸、强啡肽和锌。此外，苔藓纤维终末对抑制性神经递质GABA表现出强烈的免疫反应性。然而，此前尚未报道过苔藓纤维突触处的快速抑制性传递。在这里，我们表明，募集齿状颗粒细胞的电刺激或化学刺激会在CA3锥体神经元中引发单突触GABA(A)受体介导的突触信号。这些抑制性信号符合区分苔藓纤维-CA3突触的标准：对代谢型谷氨酸受体激动剂高度敏感、重复刺激时易化以及不依赖NMDA受体的长时程增强。从齿状回向CA3的GABA能传递不仅对进入海马体的信息流有重要意义，而且对涉及海马体的发育和病理过程也有重要意义。
