NEUROBIOLOGIC STUDIES OF NEURONS AND GLIA IN CELL CULTURE

我们以前已经表明，慢性（>24小时。）感觉刺激 神经元在体外产生生长锥敏感性的改变， 电压敏感性Ca++通道的刺激和下调 （VSCC）。 我们现在展示了这种效应的特异性， 类型的VSCC影响和不同的刺激模式。 低 电压激活型VSCC（T电流）对刺激极为敏感; 以0.5 Hz的稳定频率进行单次刺激完全消除T 电流，同时不影响高压激活（N和L）VSCC。 相同数量的冲动组织成不同的强直模式 （“突发”）或稳定刺激对N和 L电流。 放射性标记的VSCC配体PN 200 -110的结合也是 通过慢性刺激下调，证实了Ca++的数量 通道受到刺激的影响。 激活培养的骨骼肌 具有乙酰胆碱的肌细胞产生凝血酶原mRNA的增加， 这与我们提出的凝血酶在肿瘤中的作用一致。 活动依赖性突触消除的过程。 我们不能 证明丝氨酸蛋白酶抑制剂蛋白酶连接蛋白的调节 1、肌肉 如果这种内源性抑制剂确实在 突触消除可能是因为它的存在（和调制） 在一些其他细胞类型中，神经或神经胶质。 PN 1的证据 在神经胶质细胞中的存在和调节确实已经通过 布伦尼曼的小组在LDN。 研究活动无关制导的细胞定位 线索在发展中的视觉系统，我们已经建立了视网膜和 在改良的三室室中进行顶盖培养。 使用胚胎 小妞，我们已经定位了一个先前确定的厌恶成分， 顶盖神经元 我们发现了一个可能新颖的，积极的指导 放射状胶质细胞上的成分。 这两种指导机制都是 在发育过程中仅限于顶盖的一部分。

We have previously shown that chronic (>24 hr.) stimulation of sensory neurons in vitro produces an alteration in growth cone sensitivity to stimulation and a down regulation of voltage-sensitive Ca++ channels (VSCC). We now show specificity in this effect both with regard to the type of VSCC affected and for different patterns of stimulation. The low voltage activated VSCC (T current) is extremely sensitive to stimulation; single stimuli at a steady rate of 0.5 Hz completely abolish the T current while not affecting the high voltage activated (N and L) VSCC. The same number of impulses organized into different patterns of tetanic ('bursty') or steady stimulations have differential effects on the N and L currents. Binding of a radio-labelled VSCC ligand, PN200-110 is also down regulated by chronic stimulation confirming that the number of Ca++ channels is affected by the stimulation. Activation of cultured skeletal muscle cells with acetylcholine produces an increase in prothrombin mRNA, which is consistent with the role we have proposed for thrombin in the process of activity dependent synapse elimination. We fail to demonstrate a modulation of the serine protease inhibitor Protease Nexin 1 in muscle, however. If this endogenous inhibitor does play a role in synapse elimination it may be because of its presence (and modulation) in some other cell type, either nerve or glia. Evidence for PN 1's presence and modulation in glia cells has indeed been obtained by Brenneman's group in the LDN. To investigate the cellular localization of activity-independent guidance cues in the developing visual system, we have established retinal and tectal cultures in modified 3-compartment chambers. Using embryonic chick we have localized a previously identified aversive component to tectal neurons. We have discovered a possibly novel, positive guidance component on radial glia. Both of these guidance mechanisms are restricted to one portion of the tectum during development.