Department of Neurobiology and Behavior, SUNY-Stony Brook, Stony Brook, NY 11794, USA.
Eur J Neurosci. 2010 Sep;32(6):997-1005. doi: 10.1111/j.1460-9568.2010.07392.x. Epub 2010 Sep 8.
We examined whether elevating levels of neurotrophin-3 (NT-3) in the spinal cord and dorsal root ganglion (DRG) would alter connections made by muscle spindle afferent fibers on motoneurons. Adeno-associated virus (AAV) serotypes AAV1, AAV2 and AAV5, selected for their tropism profile, were engineered with the NT-3 gene and administered to the medial gastrocnemius muscle in adult rats. ELISA studies in muscle, DRG and spinal cord revealed that NT-3 concentration in all tissues peaked about 3 months after a single viral injection; after 6 months NT-3 concentration returned to normal values. Intracellular recording in triceps surae motoneurons revealed complex electrophysiological changes. Moderate elevation in cord NT-3 resulted in diminished segmental excitatory postsynaptic potential (EPSP) amplitude, perhaps as a result of the observed decrease in motoneuron input resistance. With further elevation in NT-3 expression, the decline in EPSP amplitude was reversed, indicating that NT-3 at higher concentration could increase EPSP amplitude. No correlation was observed between EPSP amplitude and NT-3 concentration in the DRG. Treatment with control viruses could elevate NT-3 levels minimally resulting in measurable electrophysiological effects, perhaps as a result of inflammation associated with injection. EPSPs elicited by stimulation of the ventrolateral funiculus underwent a consistent decline in amplitude independent of NT-3 level. These novel correlations between modified NT-3 expression and single-cell electrophysiological parameters indicate that intramuscular administration of AAV(NT-3) can exert long-lasting effects on synaptic transmission to motoneurons. This approach to neurotrophin delivery could be useful in modifying spinal function after injury.
我们研究了升高脊髓和背根神经节（DRG）中的神经营养因子-3（NT-3）水平是否会改变肌梭传入纤维在运动神经元上形成的连接。选择具有亲嗜性特征的腺相关病毒（AAV）血清型 AAV1、AAV2 和 AAV5，用 NT-3 基因进行工程改造，并将其递送至成年大鼠的内侧比目鱼肌。肌肉、DRG 和脊髓中的 ELISA 研究表明，单次病毒注射后约 3 个月，所有组织中的 NT-3 浓度达到峰值；6 个月后，NT-3 浓度恢复正常。三腿肌运动神经元的细胞内记录显示出复杂的电生理变化。脊髓 NT-3 的适度升高导致节段兴奋性突触后电位（EPSP）幅度减小，这可能是由于观察到运动神经元输入电阻的降低。随着 NT-3 表达的进一步升高，EPSP 幅度的下降得到逆转，表明在更高浓度下，NT-3 可以增加 EPSP 幅度。在 DRG 中，EPSP 幅度与 NT-3 浓度之间没有观察到相关性。用对照病毒处理可以轻微升高 NT-3 水平，从而产生可测量的电生理效应，这可能是由于注射相关的炎症所致。刺激腹外侧索引起的 EPSP 幅度一致下降，与 NT-3 水平无关。这些关于修饰的 NT-3 表达与单细胞电生理参数之间的新相关性表明，AAV(NT-3) 肌肉内给药可以对运动神经元的突触传递产生持久影响。这种神经营养因子传递的方法可能有助于在损伤后改变脊髓功能。
