Molecular mechanisms of an olfactory memory relevant to species survival

雌性小鼠对它们交配的雄性小鼠的信息素形成了嗅觉记忆。这种嗅觉记忆具有关键的生物学意义，因为它可以防止随后暴露在雄性信息素中的任何东西启动神经内分泌机制，从而终止妊娠。来自陌生雄性的信息素，没有形成记忆，通过犁鼻受体激活辅助嗅觉系统，导致受孕障碍。记忆的形成依赖于交配时颈部阴道的刺激，但需要在交配后立即长时间接触雄性信息素4至6小时。记忆的形成依赖于交配诱导的副嗅球(AOB)去甲肾上腺素能终末的激活，副嗅球是副嗅觉通路中的第一个继电器。这种记忆在交配后至少持续30天。这种记忆形成的突触变化发生在aOB。在aob，二尖瓣细胞，当被犁鼻神经输入激活时，去…更多的颗粒细胞通过树-树突触释放的谷氨酸而变大。这种去极化从颗粒细胞释放出γ-氨基丁酸，进而使二尖瓣细胞超极化。最近的研究表明，二尖瓣-颗粒-树-树突触与记忆的形成有关。在本研究中，我们获得了以下结果：1.外源性一氧化氮可以诱导信息素特异性的嗅觉记忆而不交配，这种记忆至少部分是由去甲肾上腺素介导的。此外，内源性一氧化氮合酶活性的激活也会产生同样的效果。2.我们与Ichikawa、Mori和Matsuoka博士合作，证明了已形成记忆的组中二尖瓣至颗粒不对称突触的大小明显大于未形成记忆的组。3.我们先前已证明，在AOB中激活代谢性谷氨酸受体mGluR2允许形成信息素特异性记忆。初步实验表明，缺乏mGluR2的小鼠的嗅觉记忆受损。较少

Female mice form an olfactory memory of the pheromones of the male with which they mate. This olfactory memory is of critical biological importance, because it prevents any subsequent exposure to this male's pheromones from initiating neuroendocrine mechanisms that would terminate pregnancy. Pheromones from strange males, for which no memory has been formed, induce pregnacy block by activating the accessory olfactory system by way of the vomeronasal receptors. Memory formation depends on cervicovaginal stimulation at mating, but requires a prolonged exposure of 4 to 6 h to male phernomones immediately after mating. The memory formation depends on mating-induced activation of noradrenergic terminals in the accessory olfactory bulb (AOB), the first relay in the accessory olfactory pathway. This memory lasts for at least 30 days following mating. The synaptic changes underlying this memory formation occur in the AOB.In the AOB,mitral cells, when activated by vomeronasal nerve inputs, depo … More larize granule cells by means of glutamate released at the dendrodendritic synapses. This depolarization releases gamma-aminobutyric acid from the granule cells which in turn hyperpolarize the mitral cells. Recent studies have implicated the mitral-to-granule dendrodendritic synapse in the formation of the memory. In this study we have obtained the following results.1.Exogenous administration of nitric oxide can induce a pheromone-specific olfactory memory without mating, and that this memory is mediated, at least in part, by noradrenaline. In addition, activation of endogenous nitric oxide synthase activity produces the same effect.2.In collaboration with Drs.Ichikawa, Mori and Matsuoka, we demonstrate that the size of the mitral-to-granule asymmetrical synapse is significantly larger in the group that has formed the memory than in the group that has not formed the memory.3.We have previously demonstrated that activation of mGluR2, a metabotropic glutamate receptor, in the AOB permits the formation of a pheromone-specific memory. Preliminary experiments suggest impairment of the olfactory memory in mice lacking mGluR2. Less