A Synaptic Homogeneity Principle for Parvalbumin-Expressing Interneuron Synapses in the Hippocampal Dentate Gyrus

• Main Authors: Chieh-Ju Chen, 陳玠汝
• Other Authors: Cheng-Chang Lien
• Format: Others
• Language: en_US
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/59029533758991070207

碩士 === 國立陽明大學 === 神經科學研究所 === 103 === The hippocampus is a key brain structure for learning and memory. The dentate gyrus (DG) serves as a primary gate of the hippocampus. Local-circuit GABAergic inhibitory interneurons (INs) in the DG comprise a heterogeneous cell population with distinct molecular, morphological, and electrophysiological properties. Among them, parvalbumin expressing (PV+) INs are perisomatic INs that provide powerful inhibition to their downstream neurons. They also play an important role in controlling neuronal activity and therefore mediate neuronal synchronization. PV+ INs show fast-spiking (FS) firing pattern and exhibit extensive axonal arborization within the DG granule cell (GC) layer. They innervate GCs, non-FS INs, and FS INs in the GC layer with high connection rates. Although anatomical evidence suggests that PV+ INs also innervate hilar neurons (HNs), including hilar mossy cells (MCs) and hilar interneurons (HINs), the functional connections between PV+ INs and HNs remain unknown. Here, we combined optogenetics with electrophysiology to address this question. Our results showed that GCs receive strong synaptic inputs from PV+ INs compared to MCs and HINs. However, the temporal dynamics of inhibitory inputs to GCs, MCs, and HINs are not significantly different, indicating that synapses between PV+ INs and their target cells display target cell-independent short-term synaptic plasticity. Given that PV+ INs can function as a gamma oscillation generator and mediate synchronization of GCs, we next tested whether PV+ INs mediate synchronization of HNs. Our results indicate that PV+ INs can mediate synchronization of HNs, depending on the strength of inhibitory connections and postsynaptic HN identities.