Friedman Daniel, Strowbridge Ben W
Department of Neurosciences, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA.
J Neurophysiol. 2003 May;89(5):2601-10. doi: 10.1152/jn.00887.2002.
Odor perception depends on a constellation of molecular, cellular, and network interactions in olfactory brain areas. Recently, there has been better understanding of the cellular and molecular mechanisms underlying the odor responses of neurons in the olfactory epithelium, the first-order olfactory area. In higher order sensory areas, synchronized activity in networks of neurons is known to be a prominent feature of odor processing. The perception and discrimination of odorants is associated with fast (20-70 Hz) electroencephalographic oscillations. The cellular mechanisms underlying these fast network oscillations have not been defined. In this study, we show that synchronous fast oscillations can be evoked by brief electrical stimulation in the rat olfactory bulb in vitro, partially mimicking the natural response of this brain region to sensory input. Stimulation induces periodic inhibitory synaptic potentials in mitral cells and prolonged spiking in GABAergic granule cells. Repeated stimulation leads to the persistent enhancement in both granule cell activity and mitral cell inhibition. Prominent oscillations in field recordings indicate that stimulation induces high-frequency activity throughout networks of olfactory bulb neurons. Network synchronization results from chemical and electrical synaptic interactions since both glutamate-receptor antagonists and gap junction inhibitors block oscillatory intracellular and field responses. Our results demonstrate that the olfactory bulb can generate fast oscillations autonomously through the persistent activation of networks of inhibitory interneurons. These local circuit interactions may be critically involved in odor processing in vivo.
气味感知取决于嗅觉脑区中一系列分子、细胞和网络间的相互作用。最近，人们对嗅觉上皮（一级嗅觉区域）中神经元气味反应背后的细胞和分子机制有了更深入的了解。在更高阶的感觉区域，神经元网络中的同步活动是气味处理的一个显著特征。气味剂的感知和辨别与快速（20 - 70赫兹）脑电图振荡有关。这些快速网络振荡背后的细胞机制尚未明确。在本研究中，我们表明，在体外对大鼠嗅球进行短暂电刺激可诱发同步快速振荡，部分模拟了该脑区对感觉输入的自然反应。刺激在二尖瓣细胞中诱导周期性抑制性突触电位，并在γ-氨基丁酸能颗粒细胞中延长放电。重复刺激导致颗粒细胞活性和二尖瓣细胞抑制的持续增强。场记录中的显著振荡表明，刺激在整个嗅球神经元网络中诱导高频活动。网络同步源于化学和电突触相互作用，因为谷氨酸受体拮抗剂和缝隙连接抑制剂均可阻断振荡性细胞内反应和场反应。我们的结果表明，嗅球可通过抑制性中间神经元网络的持续激活自主产生快速振荡。这些局部回路相互作用可能在体内气味处理中起关键作用。
