Gafurova Chulpan R, Tsentsevitsky Andrei N, Petrov Alexey M
Laboratory of Biophysics of Synaptic Processes, Kazan Institute of Biochemistry and Biophysics, Federal Research Center "Kazan Scientific Center of RAS", 2/31 Lobachevsky Street, Box 30, Kazan, Russia, 420111.
Kazan State Medial University, 49 Butlerova Street, Kazan, Russia, 420012.
Cell Mol Neurobiol. 2023 Mar;43(2):729-739. doi: 10.1007/s10571-022-01202-x. Epub 2022 Feb 3.
Nerve terminals contain numerous synaptic vesicles (SVs) whose exo-endocytic cycling maintains neurotransmitter release. SVs may have different properties, thereby constituting separate pools. However, behavior of SV pools remains elusive in many synapses. To fill this gap, we studied the functioning of SV pools at both low- and higher-frequency stimulations utilizing microelectrode recording and dual-labeling of SVs with FM-dyes at the mice motor nerve terminals. It was found that higher-frequency stimulation caused exocytosis of different kinds of SVs. One type of SVs contributed to exocytosis exclusively at intense activities and their exocytotic rate was depended on the order in which these SVs were recovered by endocytosis. Another type of SVs can sustain the release in response to both low- and higher-frequency stimulations, but increasing activity did not lead to enhanced exocytotic rate of these SVs. In addition, depression of neurotransmitter release induced by 20 Hz stimulation occurred independent on previous episode of 10 Hz activity. We suggest that during prolonged stimulation at least two SV pools can operate. One termed "house-keeping" that would be active at different frequencies and the other termed "plug-in" that would respond to increasing activity.
神经末梢含有大量突触小泡（SVs），其外排-内吞循环维持神经递质的释放。突触小泡可能具有不同的特性，从而构成不同的池。然而，在许多突触中，突触小泡池的行为仍然难以捉摸。为了填补这一空白，我们利用微电极记录和用FM染料对小鼠运动神经末梢的突触小泡进行双重标记，研究了低频和高频刺激下突触小泡池的功能。研究发现，高频刺激会导致不同类型突触小泡的胞吐作用。一种类型的突触小泡仅在强烈活动时参与胞吐作用，其胞吐速率取决于这些突触小泡通过内吞作用回收的顺序。另一种类型的突触小泡能够在低频和高频刺激下维持释放，但活动增加并不会导致这些突触小泡胞吐速率的提高。此外，20Hz刺激引起的神经递质释放抑制与先前的10Hz活动无关。我们认为，在长时间刺激过程中，至少有两个突触小泡池在发挥作用。一个称为“维持运转”池，在不同频率下都活跃；另一个称为“插入”池，对活动增加做出反应。
