Kovács Adrienn, Baksa Brigitta, Bayasgalan Tsogbadrakh, Szentesi Péter, Csemer Andrea, Pál Balázs
Department of Physiology, Faculty of Medicine, University of Debrecen, Nagyerdei krt 98, Debrecen, Hungary.
Neuroreport. 2019 Oct 9;30(14):933-938. doi: 10.1097/WNR.0000000000001298.
Orexins are neuromodulatory peptides of the lateral hypothalamus which regulate homeostatic mechanisms including sleep-wakefulness cycles. Orexinergic actions stabilize wakefulness by acting on the nuclei of the reticular activating system, including the pedunculopontine nucleus. Orexin application to pedunculopontine neurons produces a noisy tonic inward current and an increase in the frequency and amplitudes of excitatory postsynaptic currents. In the present project, we investigated orexinergic neuromodulatory actions on astrocyte-mediated neuronal slow inward currents of pedunculopontine neurons and their relationships with tonic currents by using slice electrophysiology on preparations from mice. We demonstrated that, in contrast to several other neuromodulatory actions and in line with literature data, orexin predominantly elicited a tonic inward current. A subpopulation of the pedunculopontine neurons possessed slow inward currents. Independently from the tonic currents, actions on slow inward currents were also detected, which resembled other neuromodulatory actions: if slow inward currents were almost absent on the neuron, orexin induced an increase of the charge movements by slow inward currents, whereas if slow inward current activity was abundant on the neurons, orexin exerted inhibitory action on it. Our data support the previous findings that orexin elicits only inward currents in contrast with cannabinoid, cholinergic or serotonergic actions. Similar to the aforementioned neuromodulatory actions, orexin influences slow inward currents in a way depending on control slow inward current activity. Furthermore, we found that orexinergic actions on slow inward currents are similarly independent from its actions on tonic currents, as it was previously found with other neuromodulatory agonists.
食欲素是下丘脑外侧的神经调节肽，可调节包括睡眠-觉醒周期在内的稳态机制。食欲素能作用通过作用于网状激活系统的核团，包括脚桥核，来稳定觉醒状态。将食欲素应用于脚桥核神经元会产生嘈杂的强直内向电流，并增加兴奋性突触后电流的频率和幅度。在本项目中，我们利用小鼠脑片电生理技术，研究了食欲素能神经调节作用对脚桥核神经元星形胶质细胞介导的神经元缓慢内向电流的影响及其与强直电流的关系。我们证明，与其他几种神经调节作用相反，且与文献数据一致，食欲素主要引发强直内向电流。脚桥核神经元的一个亚群具有缓慢内向电流。独立于强直电流之外，还检测到了食欲素对缓慢内向电流的作用，这与其他神经调节作用相似：如果神经元上几乎没有缓慢内向电流，食欲素会通过缓慢内向电流诱导电荷运动增加，而如果神经元上缓慢内向电流活动丰富，食欲素则会对其产生抑制作用。我们的数据支持了先前的研究结果，即与大麻素、胆碱能或5-羟色胺能作用相反，食欲素仅引发内向电流。与上述神经调节作用类似，食欲素以一种取决于对照缓慢内向电流活动的方式影响缓慢内向电流。此外，我们发现食欲素对缓慢内向电流的作用同样独立于其对强直电流的作用，这与之前其他神经调节激动剂的情况相同。
