Brennan P A, Schellinck H M, de la Riva C, Kendrick K M, Keverne E B
Sub-department of Animal Behaviour, University of Cambridge, UK.
Neuroscience. 1998 Dec;87(3):583-90. doi: 10.1016/s0306-4522(98)00182-1.
Olfactory learning is associated with substantial neural changes at the level of the accessory and main olfactory bulb, during both pheromonal learning in mated mice and lamb odour recognition in post partum sheep. These forms of learning occur during "sensitive periods" and an important question is whether similar neural changes occur in the olfactory bulb at other times. We used a classical conditioning procedure to establish an olfactory discrimination in adult mice and then measured changes in neurotransmitter levels in the main olfactory bulb in response to the presentation of the conditioned odours. Presentation of the conditioned, but not the non-conditioned, odour resulted in significant increases in the levels of certain transmitters, including glutamate from the mitral/tufted cells, GABA from the granule and periglomerular cells and noradrenaline from the centrifugal projection from the locus coeruleus. Overall, there was a decrease in the ratio of excitatory to inhibitory neurotransmitters in the olfactory bulb in response to the conditioned, but not the non-conditioned odour. Moreover, the magnitude of the decrease in this ratio was correlated with the level of behavioural response to the conditioned odour. These findings support the hypothesis that changes in the gain of the reciprocal synapses between mitral/tufted neurons and their inhibitory interneurons are a general feature of olfactory learning.
在交配小鼠的信息素学习以及产后绵羊的羔羊气味识别过程中，嗅觉学习与副嗅球和主嗅球水平上的大量神经变化相关。这些学习形式发生在“敏感期”，一个重要的问题是在其他时间嗅球中是否会发生类似的神经变化。我们采用经典条件反射程序在成年小鼠中建立嗅觉辨别能力，然后测量主嗅球中神经递质水平对条件气味呈现的反应变化。呈现条件气味而非非条件气味会导致某些递质水平显著升高，包括来自僧帽/簇状细胞的谷氨酸、来自颗粒细胞和球周细胞的γ-氨基丁酸以及来自蓝斑离心投射的去甲肾上腺素。总体而言，对条件气味而非非条件气味的反应导致嗅球中兴奋性与抑制性神经递质的比例降低。此外，该比例下降的幅度与对条件气味的行为反应水平相关。这些发现支持了以下假设：僧帽/簇状神经元与其抑制性中间神经元之间相互突触增益的变化是嗅觉学习的一个普遍特征。
