Source data for: Presynaptic NMDARs cooperate with local spikes toward GABA release from the reciprocal olfactory bulb granule cell spine

In the rodent olfactory bulb the smooth dendrites of the principal glutamatergic mitral cells (MCs) form reciprocal dendrodendritic synapses with large spines on GABAergic granule cells (GC), where unitary release of glutamate can trigger postsynaptic local activation of voltage-gated Na+-channels (Navs), i.e. a spine spike. Can such single MC input evoke reciprocal release? We find that unitary-like activation via two-photon uncaging of glutamate causes GC spines to release GABA both synchronously and asynchronously onto MC dendrites. This release indeed requires activation of Navs and high-voltage-activated Ca2+-channels (HVACCs), but also of NMDA receptors (NMDAR). Simulations show temporally overlapping HVACC- and NMDAR-mediated Ca2+-currents during the spine spike, and ultrastructural data prove NMDAR presence within the GABAergic presynapse. The cooperative action of presynaptic NMDARs allows to implement synapse-specific, activity-dependent lateral inhibition and thus could provi...在啮齿类动物嗅球中，谷氨酸能主神经元僧帽细胞（mitral cells, MCs）的平滑树突，可与γ-氨基丁酸能颗粒细胞（GABAergic granule cells, GC）表面的大型树突棘形成交互性树突-树突突触。在此类突触中，单次谷氨酸释放可触发突触后局部的电压门控钠通道（voltage-gated Na+-channels, Navs）激活，即树突棘动作电位（棘峰电位）。那么，单个僧帽细胞的输入能否诱发交互性递质释放？本研究发现，通过双光子光解谷氨酸实现的类单次递质激活，可使颗粒细胞的树突棘向僧帽细胞树突同步与异步释放γ-氨基丁酸。此类释放确实依赖于电压门控钠通道（Navs）与高电压激活钙通道（high-voltage-activated Ca²⁺-channels, HVACCs）的激活，同时也离不开N-甲基-D-天冬氨酸受体（NMDA receptors, NMDAR）的参与。仿真实验结果显示，在棘峰电位期间，高电压激活钙通道与NMDAR介导的钙电流存在时间上的重叠；而超微结构数据证实，NMDAR存在于γ-氨基丁酸能突触前末梢内。突触前NMDAR的协同作用可实现突触特异性、活动依赖型侧抑制，因此有望...