Molecular neurobiology of olfactory learning in the land slug

我们研究了PC对于嗅觉学习是否必要。在第一个系列实验中，在双侧pc消融后7天，将蔬菜气味与奎尼丁配对，使蛞蝓产生厌恶条件反射。与假手术的鼻涕虫相比，PC病变鼻涕虫的学习成绩明显较低。在第二组实验中，首先对鼻涕虫进行条件反射，然后在不同的时间点消融pc。在PC损伤3天后进行测试时，这些鼻涕虫也表现出严重的记忆损伤。这些结果表明，PC至少对于保留或检索厌恶气味记忆是必要的。然后我们研究了蛞蝓的中枢突触是否表现出突触可塑性。单次触须神经电刺激在前脑（PC）中诱发至少3个分量的电位，并以此刺激作为测试刺激。高频刺激触须神经后，诱发电位的阳性成分增加，这种增强持续两个多小时。在PC中发现的突触可塑性可能与嗅觉学习有关。我们还筛选了大脑中受神经活动上调的基因。解剖大脑会导致神经活动的短暂上调，从而诱发几种基因的转录。通过对72对引物的差异显示分析，显示了大约10,000个条带，其中28个条带的表达水平可重复变化，其中10个条带被克隆用于进一步分析。

We examined whether the PC is necessary for olfactory learning. In the first series of experiments, slugs were aversively conditioned by pairing vegetable odor with quinidine 7 days after ablation of bilateral PCs. The slugs with PC lesions showed significantly lower scores of learning compared to sham-operated slugs. In the second series of experiments, slugs were first conditioned, and at various time points, the PCs were ablated. When tested 3 days after PC lesion, these slugs also showed severe impairment of memory. These results indicate that the PC is necessary at least for the retention or retrieval of aversive odor memories.We then investigated whether the central synapses in the slug display synaptic plasticity. A single electrical stimulation of the tentacle nerve evoked a potential in the procerebrum (PC) with at least 3 components, and this stimulus was used as the test stimulus. After a high frequency stimulation of the tentacle nerve, the positive component of the evoked potential increased, and this potentiation lasted for more than two hours. That synaptic plasticity found in the PC may be involved in olfactory learning. We also screened genes in the brain that are upregulated by neural activity. Dissecting the brain results in transient up-regulation of neural activity, and this induces transcription of several genes. By differential display analyses using 72 pairs of primers, approximately 10,000 bands were displayed and 28 showed reproducible changes in the expression levels, and 10 of these were cloned for further analysis.