Kuczewski Nicola, Fourcaud-Trocmé Nicolas, Savigner Agnès, Thevenet Marc, Aimé Pascaline, Garcia Samuel, Duchamp-Viret Patricia, Palouzier-Paulignan Brigitte
Université Lyon1, Centre de Recherche en Neurosciences de Lyon INSERM U1028/CNRS UMR5292 - Equipe Olfaction: Du codage à la mémoire, F-69366, Lyon, France
Université Lyon1, Centre de Recherche en Neurosciences de Lyon INSERM U1028/CNRS UMR5292 - Equipe Olfaction: Du codage à la mémoire, F-69366, Lyon, France.
J Physiol. 2014 Jul 1;592(13):2751-69. doi: 10.1113/jphysiol.2013.269639. Epub 2014 Apr 7.
Odour perception depends closely on nutritional status, in animals as in humans. Insulin, the principal anorectic hormone, appears to be one of the major candidates for ensuring the link between olfactory abilities and nutritional status, by modifying processing in the olfactory bulb (OB), one of its main central targets. The present study investigates whether and how insulin can act in OB, by evaluating its action on the main output neurons activities, mitral cells (MCs), in acute rat OB slices. Insulin was found to act at two OB network levels: (1) on MCs, by increasing their excitability, probably by inhibiting two voltage-gated potassium (K(+)) channels; (2) on interneurons by modifying the GABAergic and on glutamatergic synaptic activity impinging on MCs, mainly reducing them. Insulin also altered the olfactory nerve (ON)-evoked excitatory postsynaptic currents in 60% of MCs. Insulin decreased or increased the ON-evoked responses in equal proportion and the direction of its effect depended on the initial neuron ON-evoked firing rate. Indeed, insulin tended to decrease the high and to increase the low ON-evoked firing rates, thereby reducing inter-MC response firing variability. Therefore, the effects of insulin on the evoked firing rates were not carried out indiscriminately in the MC population. By constructing a mathematical model, the impact of insulin complex effects on OB was assessed at the population activity level. The model shows that the reduction of variability across cells could affect MC detection and discrimination abilities, mainly by decreasing and, less frequently, increasing them, depending on odour quality. Thus, as previously proposed, this differential action of insulin on MCs across odours would allow this hormone to put the olfactory function under feeding signal control, given the discerning valence of an odour as a function of nutritional status.
与人类一样，动物的气味感知也与营养状况密切相关。胰岛素是主要的食欲抑制激素，它似乎是确保嗅觉能力与营养状况之间联系的主要候选因素之一，通过改变其主要中枢靶点之一嗅球（OB）的处理过程来实现。本研究通过评估胰岛素对急性大鼠OB切片中主要输出神经元即二尖瓣细胞（MCs）活动的作用，来探究胰岛素是否以及如何在OB中发挥作用。研究发现胰岛素在OB网络的两个层面发挥作用：（1）作用于MCs，通过增加其兴奋性，可能是通过抑制两种电压门控钾（K(+)）通道；（2）作用于中间神经元，通过改变作用于MCs的GABA能和谷氨酸能突触活动，主要是降低这些活动。胰岛素还改变了60%的MCs中嗅神经（ON）诱发的兴奋性突触后电流。胰岛素降低或增加ON诱发反应的比例相同，其作用方向取决于初始神经元的ON诱发放电率。实际上，胰岛素倾向于降低高ON诱发放电率并增加低ON诱发放电率，从而减少MC间反应放电的变异性。因此，胰岛素对诱发放电率的影响并非在MC群体中不加区分地进行。通过构建数学模型，在群体活动水平评估了胰岛素复杂效应对OB的影响。该模型表明，细胞间变异性的降低可能会影响MC的检测和辨别能力，主要是通过降低，较少情况下也会增加，这取决于气味质量。因此，正如之前所提出的，鉴于气味作为营养状况函数的辨别效价，胰岛素对不同气味的MCs的这种差异作用将使该激素能够将嗅觉功能置于进食信号的控制之下。
