Department of Neuroanatomy and Embryology, Fukushima Medical University Graduate School of Medicine, Fukushima, Japan.
Brain Interdisciplinary Research Division, Research Institute for Science and Technology, Tokyo University of Science, Noda-shi, Japan.
Front Neural Circuits. 2018 Feb 7;12:6. doi: 10.3389/fncir.2018.00006. eCollection 2018.
Cerebellar malformations cause changes to the sleep-wake cycle, resulting in sleep disturbance. However, it is unclear how the cerebellum contributes to the sleep-wake cycle. To examine the neural connections between the cerebellum and the nuclei involved in the sleep-wake cycle, we investigated the axonal projections of Purkinje cells in the mouse posterior vermis by using an adeno-associated virus (AAV) vector (serotype rh10) as an anterograde tracer. When an AAV vector expressing humanized renilla green fluorescent protein was injected into the cerebellar lobule IX, hrGFP and synaptophysin double-positive axonal terminals were observed in the region of medial parabrachial nucleus (MPB). The MPB is involved in the phase transition from rapid eye movement (REM) sleep to Non-REM sleep and , and the cardiovascular and respiratory responses. The hrGFP-positive axons from lobule IX went through the ventral spinocerebellar tract and finally reached the MPB. By contrast, when the AAV vector was injected into cerebellar lobule VI, no hrGFP-positive axons were observed in the MPB. To examine neurons projecting to the MPB, we unilaterally injected Fast Blue and AAV vector (retrograde serotype, rAAV2-retro) as retrograde tracers into the MPB. The cerebellar Purkinje cells in lobules VIII-X on the ipsilateral side of the Fast Blue-injected MPB were retrogradely labeled by Fast Blue and AAV vector (retrograde serotype), but no retrograde-labeled Purkinje cells were observed in lobules VI-VII and the cerebellar hemispheres. These results indicated that Purkinje cells in lobules VIII-X directly project their axons to the ipsilateral MPB but not lobules VI-VII. The direct connection between lobules VIII-X and the MPB suggests that the cerebellum participates in the neural network controlling the sleep-wake cycle, and cardiovascular and respiratory responses, by modulating the physiological function of the MPB.
小脑畸形会导致睡眠-觉醒周期发生变化，从而导致睡眠障碍。然而，小脑如何参与睡眠-觉醒周期尚不清楚。为了研究小脑与睡眠-觉醒周期相关核团之间的神经连接，我们使用腺相关病毒（AAV）载体（血清型 rh10）作为顺行示踪剂，研究了小鼠后蚓部浦肯野细胞的轴突投射。当将表达人源化海肾荧光素酶的 AAV 载体注射到小脑小叶 IX 时，在中脑臂旁核（MPB）区域观察到海肾荧光素酶和突触小体蛋白双阳性的轴突末梢。MPB 参与从快速眼动（REM）睡眠到非快速眼动（NREM）睡眠的相位转换，以及心血管和呼吸反应。来自小叶 IX 的海肾荧光素酶阳性轴突穿过腹侧脊髓小脑束，最终到达 MPB。相比之下，当 AAV 载体被注射到小脑小叶 VI 时，在 MPB 中没有观察到海肾荧光素酶阳性轴突。为了研究投射到 MPB 的神经元，我们将 Fast Blue 和 AAV 载体（逆行血清型，rAAV2-retro）单侧注射到 MPB 中作为逆行示踪剂。Fast Blue 注射的 MPB 同侧的小叶 VIII-X 的小脑浦肯野细胞被 Fast Blue 和 AAV 载体（逆行血清型）逆行标记，但在小叶 VI-VII 和小脑半球中没有观察到逆行标记的浦肯野细胞。这些结果表明，小叶 VIII-X 的浦肯野细胞直接将其轴突投射到同侧的 MPB，但不投射到小叶 VI-VII。小叶 VIII-X 与 MPB 之间的直接连接表明，小脑通过调节 MPB 的生理功能，参与控制睡眠-觉醒周期以及心血管和呼吸反应的神经网络。
