Neuroscience Program and Department of Physiology and Biophysics, University of Colorado, Anschutz Medical Campus, Aurora, Colorado 80045, USA.
J Neurosci. 2013 Jan 23;33(4):1552-63. doi: 10.1523/JNEUROSCI.3410-12.2013.
Lateral inhibition between neurons occurs in many different sensory systems, where it can perform such functions as contrast enhancement. In the olfactory bulb, lateral inhibition may occur between odorant receptor-specific glomeruli that are linked anatomically by GABAergic granule cells (GCs) and cells within the glomerular layer, although evidence supporting lateral inhibition at a functional level is modest. Here, we used patch-clamp, imaging, and glutamate uncaging methods in rat olfactory bulb slices to test for the presence of interglomerular lateral inhibition, as well as its underlying mechanisms. We found that a conditioning stimulus applied at one or a small group of glomeruli could suppress stimulus-evoked excitation of output mitral cells (MCs) at another glomerulus for interstimulus intervals of 20-50 ms and glomerular separations of up to 600 μm. The observed lateral inhibition was entirely dependent on circuitry within the glomerular layer, rather than GCs, and it involved GABAergic synaptic inputs that were targeted mainly onto tufted cells, which act as intermediaries in the excitation between olfactory sensory neurons and MCs. The key cell type responsible for mediating lateral interactions between glomeruli were GABAergic short-axon cells. These results suggest a functional segregation of GABAergic cells within the bulb, with one set located in the glomerular layer mediating suppression of MC spiking across glomeruli, and a second set, the GCs, synchronizing different glomeruli.
神经元之间的侧抑制存在于许多不同的感觉系统中，它可以执行增强对比度等功能。在嗅球中，侧抑制可能发生在通过 GABA 能颗粒细胞 (GCs) 和颗粒细胞层内的细胞在解剖上连接的特定气味受体的肾小球之间，尽管支持功能水平的侧抑制的证据是适度的。在这里，我们使用大鼠嗅球切片中的膜片钳、成像和谷氨酸非笼锁方法来测试肾小球间侧抑制的存在及其潜在机制。我们发现，在 20-50ms 的刺激间隔和高达 600μm 的肾小球分离度下，在一个或一小群肾小球上施加的条件刺激可以抑制另一个肾小球上的输出僧帽细胞 (MCs) 的刺激诱发兴奋。观察到的侧抑制完全依赖于肾小球层内的回路，而不是 GCs，它涉及 GABA 能突触输入，主要靶向于作为嗅感觉神经元和 MCs 之间兴奋的中间神经元的丛状细胞。介导肾小球间侧向相互作用的关键细胞类型是 GABA 能短轴细胞。这些结果表明，在球体内存在 GABA 能细胞的功能分离，一组位于肾小球层内，介导跨肾小球的 MC 放电抑制，另一组是 GCs，同步不同的肾小球。
