Yang Jian-Chang, Fan Xiao-Li, Song Xin-Ai, Li Qiang
Department of Physiology and Pathophysiology, Xi'an Jiaotong University School of Medicine, Xi'an Yanta Street W 76#, Xi'an, Shaanxi 710061, China.
Neurosci Lett. 2008 Dec 31;448(3):255-9. doi: 10.1016/j.neulet.2008.10.044. Epub 2008 Oct 17.
The present study investigates changes in red nucleus (RN) neuronal activity and the role of glutamate receptors (GluRs) after simulated microgravity (tail-suspension) in the rat using single-unit recording and microinjection. The results showed that tail-suspension for 3, 7, and 14 days could induce a significant decrease in spontaneous firing rate of RN neurons in a time-dependent manner. Unilateral microinjection of glutamate into the RN significantly increased the firing rate of RN neurons, but the increased firing rate was significantly reduced following tail-suspension time. Microinjection of the NMDA receptor antagonist MK-801 or the non-NMDA receptor antagonist DNQX into the RN blocked this excitatory effect induced by glutamate. However, microinjection of the metabotropic glutamate receptor (mGluR) antagonist (+/-)-MCPG into the RN had no effect. These results suggest that simulated microgravity can reduce excitability of RN neurons following a functional impairment of glutamate receptors. NMDA and non-NMDA receptors, but not mGluRs, are involved in the mediation of glutamate-evoked excitation of RN neurons. The decrease in excitability of RN neurons may be involved in simulated microgravity-induced muscle atrophy.
本研究采用单单位记录和微注射技术，研究了模拟微重力（尾部悬吊）后大鼠红核（RN）神经元活动的变化以及谷氨酸受体（GluRs）的作用。结果表明，尾部悬吊3天、7天和14天可导致RN神经元的自发放电率随时间呈显著下降。向RN单侧微注射谷氨酸可显著提高RN神经元的放电率，但随着尾部悬吊时间的延长，增加的放电率显著降低。向RN微注射NMDA受体拮抗剂MK-801或非NMDA受体拮抗剂DNQX可阻断谷氨酸诱导的这种兴奋作用。然而，向RN微注射代谢型谷氨酸受体（mGluR）拮抗剂（+/-）-MCPG则没有效果。这些结果表明，模拟微重力可在谷氨酸受体功能受损后降低RN神经元的兴奋性。NMDA和非NMDA受体而非mGluRs参与介导谷氨酸诱发的RN神经元兴奋。RN神经元兴奋性的降低可能与模拟微重力诱导的肌肉萎缩有关。
