Fourcaud-Trocmé Nicolas, Briffaud Virginie, Thévenet Marc, Buonviso Nathalie, Amat Corine
INSERM U1028, CNRS UMR5292, Centre de Recherche en Neurosciences de Lyon, Equipe CMO, Université Lyon 1, Lyon, France.
J Neurophysiol. 2018 Jan 1;119(1):274-289. doi: 10.1152/jn.00053.2017. Epub 2017 Oct 11.
In mammals, olfactory bulb (OB) dynamics are paced by slow and fast oscillatory rhythms at multiple levels: local field potential, spike discharge, and/or membrane potential oscillations. Interactions between these levels have been well studied for the slow rhythm linked to animal respiration. However, less is known regarding rhythms in the fast beta (10-35 Hz) and gamma (35-100 Hz) frequency ranges, particularly at the membrane potential level. Using a combination of intracellular and extracellular recordings in the OB of freely breathing rats, we show that beta and gamma subthreshold oscillations (STOs) coexist intracellularly and are related to extracellular local field potential (LFP) oscillations in the same frequency range. However, they are differentially affected by changes in cell excitability and by odor stimulation. This leads us to suggest that beta and gamma STOs may rely on distinct mechanisms: gamma STOs would mainly depend on mitral cell intrinsic resonance, while beta STOs could be mainly driven by synaptic activity. In a second study, we find that STO occurrence and timing are constrained by the influence of the slow respiratory rhythm on mitral and tufted cells. First, respiratory-driven excitation seems to favor gamma STOs, while respiratory-driven inhibition favors beta STOs. Second, the respiratory rhythm is needed at the subthreshold level to lock gamma and beta STOs in similar phases as their LFP counterparts and to favor the correlation between STO frequency and spike discharge. Overall, this study helps us to understand how the interaction between slow and fast rhythms at all levels of OB dynamics shapes its functional output. NEW & NOTEWORTHY In the mammalian olfactory bulb of a freely breathing anesthetized rat, we show that both beta and gamma membrane potential fast oscillation ranges exist in the same mitral and tufted (M/T) cell. Importantly, our results suggest they have different origins and that their interaction with the slow subthreshold oscillation (respiratory rhythm) is a key mechanism to organize their dynamics, favoring their functional implication in olfactory bulb information processing.
在哺乳动物中，嗅球（OB）的动态变化在多个层面上由缓慢和快速振荡节律调节：局部场电位、动作电位发放和/或膜电位振荡。对于与动物呼吸相关的缓慢节律，这些层面之间的相互作用已得到充分研究。然而，对于快速β（10 - 35赫兹）和γ（35 - 100赫兹）频率范围内的节律，尤其是在膜电位层面，人们了解较少。通过在自由呼吸大鼠的嗅球中结合细胞内和细胞外记录，我们发现β和γ阈下振荡（STOs）在细胞内共存，并且与相同频率范围内的细胞外局部场电位（LFP）振荡相关。然而，它们受到细胞兴奋性变化和气味刺激的不同影响。这使我们认为β和γ STOs可能依赖于不同的机制：γ STOs主要依赖于二尖瓣细胞的固有共振，而β STOs可能主要由突触活动驱动。在第二项研究中，我们发现STO的发生和时间受缓慢呼吸节律对二尖瓣和簇状细胞影响的限制。首先，呼吸驱动的兴奋似乎有利于γ STOs，而呼吸驱动的抑制有利于β STOs。其次，在阈下水平需要呼吸节律来将γ和β STOs锁定在与其LFP对应物相似的相位，并有利于STO频率与动作电位发放之间的相关性。总体而言，这项研究有助于我们理解嗅球动态变化各个层面上缓慢和快速节律之间的相互作用如何塑造其功能输出。新发现与值得注意之处 在自由呼吸的麻醉大鼠的哺乳动物嗅球中，我们表明β和γ膜电位快速振荡范围存在于相同的二尖瓣和簇状（M/T）细胞中。重要的是，我们的结果表明它们有不同的起源，并且它们与缓慢阈下振荡（呼吸节律）的相互作用是组织其动态变化的关键机制，有利于它们在嗅球信息处理中的功能作用。
