Analysis of mechanisms of pheromonal memory formation

当雌性老鼠交配时，它们对交配雄性的信息素形成嗅觉记忆。这种记忆背后的神经变化发生在副嗅球（AOB），依赖于交配诱导的释放去甲肾上腺素（NA）的AOB和涉及二尖瓣和颗粒细胞之间的相互突触的变化。在本研究中，我们得到了以下结果.原位杂交实验表明，在记忆形成过程中，AOB中存在信息素特异性激活神经元型一氧化氮合酶mRNA的作用，可能参与调节中间突触过程.利用小鼠AOB切片，我们证明了N-甲基-D-天冬氨酸受体和II型代谢型谷氨酸受体在AOB二尖瓣细胞的树突反馈抑制中的相反作用.在体电生理实验表明，刺激阴道神经鞘可通过减少相互的树-树抑制来增强AOB二尖瓣细胞的活性.行为学和免疫组化分析表明，神经胶质细胞在信息素记忆的形成中起着重要作用。此外，我们还观察了小鼠嗅球中谷氨酰胺合成酶和小胶质细胞特异性离子钙结合衔接蛋白（Iba 1）的免疫组化表达模式.作为进一步探索信息素记忆的详细机制，我们简化了神经元回路的分析，通过重建初级分离培养的AOB神经元中二尖瓣和颗粒细胞之间的树突突触。使用这个体外系统，我们证明NA通过突触前机制降低二尖瓣细胞中GABA能抑制性突触后电流。在体内和体外的电生理实验表明，神经甾体脱氢表雄酮和催产素的调节作用，在嗅球的二尖瓣和颗粒细胞之间的突触传递。

When female mice were mated, they form an olfactory memory to the pheromones of the mating male. The neural changes underlying this memory occur in the accessory olfactory bulb (AOB), depend upon mating-induced release of noradrenaline (NA) in the AOB and involve changes at the reciprocal synapses between mitral and granule cells. In this study we have obtained the following results.1. In situ hybridization experiments suggest that there is a pheromone-specific activation of neuronal nitric oxide synthase mRNA in the AOB during memory formation which may regulate intermediate synaptic processes.2. Using slices of the mouse AOB, we demonstrated opposite roles for N-methyl-D-aspartate receptors and group II metabotropic glutamate receptors in the dendrodendritic feedback inhibition of AOB mitral cells.3. In vivo electrophysiological experiments showed that vaginocervical stimulation enhances the activity of AOB mitral cells through a reduction in reciprocal dendrodendritic inhibition.4. Behavioural and immunohistochemical analyses demonstrated an important role for glial cells in the formation of pheromonal memory. In addition, we showed immunohistochemical expression patterns of glutamine synthetase and microglia-specific ionized calcium binding adaptor protein (Iba 1) in the mouse olfactory bulb.5. As a further step in exploring the detailed mechanisms underlying the pheromonal memory, we have simplified the analysis of neuronal circuit by reconstituting the dendrodendritic synapse between mitral and granule cells in primary dissociated cultures of AOB neurons. Using this in vitro system, we demonstrated that NA reduces GABAergic inhibitory postsynaptic currents in mitral cells by a presynaptic mechanism.6. In vivo and in vitro electrophysiological experiments demonstrated modulatory actions of the neurosteroid dehydroepiandrosterone and oxytocin on synaptic transmission between mitral and granule cells in the olfactory bulb.