Institute of Neuroscience, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK.
University of Louisville, Louisville, KY, USA.
Eur J Neurosci. 2018 Oct;48(8):2807-2815. doi: 10.1111/ejn.13773. Epub 2018 Jan 10.
Avian and mammalian brains have evolved independently from each other for about 300 million years. During that time, the hippocampal formation (HF) has diverged in morphology and cytoarchitecture, but seems to have conserved much of its function. It is therefore an open question how seemingly different neural organizations can generate the same function. A prominent feature of the mammalian hippocampus is that it generates different neural oscillations, including the gamma rhythm, which plays an important role in memory processing. In this study, we investigate whether the avian hippocampus also generates gamma oscillations, and whether similar pharmacological mechanisms are involved in this function. We investigated the existence of gamma oscillations in avian HF using in vitro electrophysiology in P0-P12 domestic chick (Gallus gallus domesticus) HF brain slices. Persistent gamma frequency oscillations were induced by the bath application of the cholinergic agonist carbachol, but not by kainate, a glutamate receptor agonist. Similar to other species, carbachol-evoked gamma oscillations were sensitive to GABA , AMPA/kainate and muscarinic (M1) receptor antagonism. Therefore, similar to mammalian species, muscarinic receptor-activated avian HF gamma oscillations may arise via a pyramidal-interneuron gamma (PING)-based mechanism. Gamma oscillations are most prominent in the ventromedial area of the hippocampal slices, and gamma power is reduced more laterally and dorsally in the HF. We conclude that similar micro-circuitry may exist in the avian and mammalian hippocampal formation, and this is likely to relate to the shared function of the two structures.
鸟类和哺乳动物的大脑已经各自独立进化了大约 3 亿年。在此期间，海马结构（HF）在形态和细胞构筑上已经发生了分歧，但似乎保留了其大部分功能。因此，一个悬而未决的问题是，看似不同的神经组织如何产生相同的功能。哺乳动物海马体的一个突出特征是它会产生不同的神经振荡，包括伽马节律，它在记忆处理中起着重要作用。在这项研究中，我们研究了鸟类海马体是否也会产生伽马振荡，以及是否涉及类似的药理学机制。我们通过在体电生理学研究，在 P0-P12 日龄家鸡（Gallus gallus domesticus）海马脑片中研究了鸟类 HF 中伽马振荡的存在。持续的伽马频率振荡是通过巴氯芬（一种胆碱能激动剂）的浴内应用诱导的，但不是通过红藻氨酸（一种谷氨酸受体激动剂）诱导的。与其他物种类似，巴氯芬诱导的伽马振荡对 GABA、AMPA/kainate 和毒蕈碱（M1）受体拮抗剂敏感。因此，与哺乳动物物种类似，毒蕈碱受体激活的鸟类 HF 伽马振荡可能通过锥体神经元-中间神经元伽马（PING）为基础的机制产生。伽马振荡在海马体切片的腹内侧区域最为明显，在 HF 的外侧和背侧，伽马功率降低更为明显。我们得出结论，类似的微电路可能存在于鸟类和哺乳动物的海马结构中，这可能与这两个结构的共享功能有关。
