Agents that positively modulate the activity of α7nAChRs are used as cognitive enhancers and for the treatment of hippocampus-dependent functional decline. However, it is not known whether the expression and the effects of α7nAChRs apply to the entire longitudinal axis of the hippocampus equally. Given that cholinergic system-involving hippocampal functions are not equally distributed along the hippocampus, we comparatively examined the expression and the effects of α7nAChRs on excitatory synaptic transmission between the dorsal and the ventral hippocampal slices from adult rats. We found that α7nAChRs are equally expressed in the CA1 field of the two segments of the hippocampus. However, activation of α7nAChRs by their highly selective agonist PNU 282987 induced a gradually developing increase in field excitatory postsynaptic potential only in the dorsal hippocampus. This long-term potentiation was not reversed upon application of nonselective nicotinic receptor antagonist mecamylamine, but the induction of potentiation was prevented by prior blockade of α7nAChRs by their antagonist MG 624. In contrast to the long-term synaptic plasticity, we found that α7nAChRs did not modulate short-term synaptic plasticity in either the dorsal or the ventral hippocampus. These results may have implications for the role that α7nAChRs play in specifically modulating functions that depend on the normal function of the dorsal hippocampus. We propose that hippocampal functions that rely on a direct α7 nAChR-mediated persistent enhancement of glutamatergic synaptic transmission are preferably supported by dorsal but not ventral hippocampal synapses.

中文翻译：

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α7烟碱乙酰胆碱受体诱导背侧海马而非腹侧海马的长期突触增强

积极调节 α7nAChR 活性的药物可用作认知增强剂并用于治疗海马依赖性功能衰退。然而，尚不清楚 α7nAChR 的表达和作用是否同样适用于海马的整个纵轴。鉴于涉及海马功能的胆碱能系统在海马上的分布并不均匀，我们比较研究了α7nAChRs对成年大鼠背侧和腹侧海马切片之间兴奋性突触传递的表达和影响。我们发现α7nAChRs在海马两段的CA1区中表达相同。然而，α7nAChR 的高选择性激动剂 PNU 282987 激活仅在背侧海马中诱导场兴奋性突触后电位逐渐增加。应用非选择性烟碱受体拮抗剂美加明后，这种长期增强作用并未逆转，但通过其拮抗剂 MG 624 预先阻断 α7nAChRs，可以阻止增强作用的诱导。与长期突触可塑性相反，我们发现 α7nAChRs不调节背侧或腹侧海马的短期突触可塑性。这些结果可能对 α7nAChR 在依赖于背侧海马正常功能的特异性调节功能中发挥的作用有影响。我们认为，依赖于直接 α7 nAChR 介导的谷氨酸能突触传递持续增强的海马功能最好由背侧海马突触支持，而不是腹侧海马突触。