Department of Physiology, Showa University School of Medicine, Tokyo, Japan.
Faculty of Health Sciences, Aomori University of Health and Welfare, Aomori, Japan; Clinical Research Center, Murayama Medical Center, Musashimurayama, Tokyo, Japan.
Neuroscience. 2023 Sep 15;528:89-101. doi: 10.1016/j.neuroscience.2023.08.002. Epub 2023 Aug 7.
Proteinase-activated receptor-1 (PAR1) is expressed in astrocytes of various brain regions, and its activation is involved in the modulation of neuronal activity. Here, we report effects of PAR1 selective agonist TFLLR on respiratory rhythm generation in brainstem-spinal cord preparations. Preparations were isolated from newborn rats (P0-P4) under deep isoflurane anesthesia and were transversely cut at the rostral medulla. Preparations were superfused with artificial cerebrospinal fluid (25-26 °C), and inspiratory C4 ventral root activity was monitored. The responses to TFLLR of cells close to the cut surface were detected by calcium imaging or membrane potential recordings. Application of 10 μM TFLLR (4 min) induced a rapid and transient increase of calcium signal in cells of the ventrolateral respiratory regions of the medulla. More than 88% of responding cells (223/254 cells from 13 preparations) were also activated by low (0.2 mM) K solution, suggesting that they were astrocytes. Immunohistochemical examination demonstrated that PAR1 was expressed on many astrocytes. Respiratory-related neurons in the medulla were transiently hyperpolarized (-1.8 mV) during 10 μM TFLLR application, followed by weak membrane depolarization after washout. C4 burst rate decreased transiently in response to application of TFLLR, followed by a slight increase. The inhibitory effect was partially blocked by 50 μM theophylline. In conclusion, activation of astrocytes via PAR1 resulted in a decrease of inspiratory C4 burst rate in association with transient hyperpolarization of respiratory-related neurons. After washout, slow and weak excitatory responses appeared. Adenosine may be partially involved in the inhibitory effect of PAR1 activation.
蛋白酶激活受体-1（PAR1）在大脑各个区域的星形胶质细胞中表达，其激活参与了神经元活动的调节。在这里，我们报告 PAR1 选择性激动剂 TFLLR 对脑干-脊髓脑片呼吸节律产生的影响。脑片在深度异氟烷麻醉下从新生大鼠（P0-P4）中分离出来，并在延髓的颅侧进行横切。脑片用人工脑脊液（25-26°C）灌流，监测吸气 C4 腹根活动。通过钙成像或膜电位记录检测靠近切面的细胞对 TFLLR 的反应。应用 10 μM TFLLR（4 分钟）会在延髓的腹外侧呼吸区的细胞中迅速产生短暂的钙信号增加。超过 88%（13 个脑片的 223/254 个细胞）的反应细胞也被低浓度（0.2mM）K 溶液激活，表明它们是星形胶质细胞。免疫组织化学检查表明 PAR1 表达在许多星形胶质细胞上。在应用 10 μM TFLLR 期间，延髓中的呼吸相关神经元被短暂地超极化（-1.8mV），随后在冲洗后出现微弱的膜去极化。应用 TFLLR 会使 C4 爆发率短暂下降，随后略有增加。抑制作用部分被 50 μM 茶碱阻断。总之，通过 PAR1 激活星形胶质细胞会导致吸气 C4 爆发率降低，同时伴有呼吸相关神经元的短暂超极化。冲洗后，会出现缓慢而微弱的兴奋反应。腺苷可能部分参与了 PAR1 激活的抑制作用。
