Graduate Program in Physiology and Biophysics, Department of Pharmacology & Physiology, Georgetown University, Washington, DC 20007, USA.
J Neurosci. 2013 Aug 28;33(35):14075-86. doi: 10.1523/JNEUROSCI.0692-13.2013.
The principle neurons of the striatum are GABAergic medium spiny neurons (MSNs), whose collateral synapses onto neighboring neurons play critical roles in striatal function. MSNs can be divided by dopamine receptor expression into D1-class and D2-class MSNs, and alterations in D2 MSNs are associated with various pathological states. Despite overwhelming evidence for D2 receptors (D2Rs) in maintaining proper striatal function, it remains unclear how MSN collaterals are specifically altered by D2R activation. Here, we report that chronic D2R stimulation regulates MSN collaterals in vitro by presynaptic and postsynaptic mechanisms. We used corticostriatal cultures from mice in which MSN subtypes were distinguished by fluorophore expression. Quinpirole, an agonist for D2/3 receptors, was used to chronically activate D2Rs. Quinpirole increased the rate and strength of collateral formation onto D2R-containing MSNs as measured by dual whole-cell patch-clamp recordings. Additionally, these neurons were more sensitive to low concentrations of GABA and exhibited an increase in gephyrin puncta density, suggesting increased postsynaptic GABAA receptors. Last, quinpirole treatment increased presynaptic GABA release sites, as shown by increased frequency of sIPSCs and mIPSCs, correlating with increased VGAT (vesicular GABA transporter) puncta. Combined with the observation that there were no detectable differences in sensitivity to specific GABAA receptor modulators, we provide evidence that D2R activation powerfully transforms MSN collaterals via coordinated presynaptic and postsynaptic alterations. As the D2 class of MSNs is highly implicated in Parkinson's disease and other neurological disorders, our findings may contribute to understanding and treating the changes that occur in these pathological states.
纹状体的主要神经元是 GABA 能中型棘突神经元（MSNs），其旁突与邻近神经元的突触在纹状体功能中起着关键作用。MSNs 可以根据多巴胺受体表达分为 D1 类和 D2 类 MSNs，D2 类 MSNs 的改变与各种病理状态有关。尽管有大量证据表明 D2 受体（D2Rs）在维持适当的纹状体功能中起作用，但仍不清楚 D2R 激活如何特异性改变 MSN 侧突。在这里，我们报告慢性 D2R 刺激通过突触前和突触后机制调节体外 MSN 侧突。我们使用了来自小鼠的皮质纹状体培养物，其中 MSN 亚型通过荧光蛋白表达来区分。喹吡罗，一种 D2/3 受体激动剂，用于慢性激活 D2R。喹吡罗增加了包含 D2R 的 MSN 上侧突形成的速度和强度，这是通过双全细胞膜片钳记录来测量的。此外，这些神经元对低浓度 GABA 更敏感，并表现出 Gephyrin 棘突密度增加，表明突触后 GABAA 受体增加。最后，喹吡罗处理增加了 GABA 释放位点的突触前，如 sIPSCs 和 mIPSCs 频率增加，与 VGAT（囊泡 GABA 转运体）棘突增加相关。结合观察到对特定 GABAA 受体调节剂的敏感性没有可检测到的差异，我们提供了证据表明 D2R 激活通过协调的突触前和突触后改变有力地改变 MSN 侧突。由于 D2 类 MSNs 高度涉及帕金森病和其他神经疾病，我们的发现可能有助于理解和治疗这些病理状态中发生的变化。
