Mechanisms of formation, maintenance and extinction of olfactory learning

雌性小鼠学会识别与它们交配的雄性小鼠的尿液信息素。这种嗅觉学习与副嗅球(AOB)的实质性神经变化有关，AOB是犁鼻系统的第一个中继器。我们在脑片上发现，在间隔和长期刺激二尖瓣细胞轴突后，从二尖瓣细胞(一类单一的投射神经元)到颗粒细胞抑制性中间神经元的谷氨酸能传递显示出与信息素学习相同的基本特征的长时程增强(LTP)，去甲肾上腺素通过突触前α_2肾上腺素能受体介导的抑制谷氨酸释放而增强LTP的诱导，由于去极化平台的减少，使突触后细胞在Theta频率刺激序列中释放更多的动作电位。我们的发现为去甲肾上腺素调节嗅觉学习提供了一个独特的细胞机制。在出生后第12天，幼年大鼠表现出对某种气味的厌恶，并在出生后第11天出现足部电击。我们表明，幼年大鼠嗅球(OB)中的有丝分裂原激活蛋白激酶/细胞外信号调节激酶(MAPK/ERK)-环磷酸腺苷反应元件结合蛋白(CREB)通路是长期需要的，但不是短期的，促进大鼠厌恶嗅觉学习的过程。我们还发现OB区的GABA_A和GABA_B受体都参与了厌恶嗅觉学习的调节。

Female mice learn to recognize the urinary pheromones of the male with which they mate. This olfactory learning is associated with substantial neural changes in the accessory olfactory bulb(AOB), first relay in the vomeronasal system. We show in AOB slices that glutamatergic transmission from mitral cells, a single class of projection neurons, to granule cell inhibitory interneurons, displays long-term potentiation(LTP), which shares essential features with pheromonal learning, following spaced and long-term theta frequency stimulation of mitral cell axons and that noradrenaline enhances the induction of LTP via presynaptic α_2-adrenergic receptor-mediated inhibition of glutamate release that allows the postsynaptic cell to fire more action potentials during theta frequency stimulus train due to a reduction in depolarising plateau. Our findings provide a unique cellular mechanism for the noradrenergic modulation of olfactory learning.On postnatal day 12, young rats show an aversion to an odor to which they has been exposed along with presentation of foot shock on postnatal day 11. We show that the mitogen-activated protein kinase/extracellular-signal regulated kinase(MAPK/ERK)-cyclic AMP response element binding protein(CREB) pathway in the olfactory bulb(OB) is required for the long-term, but not the short-term, facilitation process of aversive olfactory learning in young rats. We also show that both of GABA_A and GABA_B reeptors in the OB are involved in the regulation of aversive olfactory learning.