PRESYNAPTIC RECEPTORS ON EMBRYONIC SENSORY NEURONS

近年来，一种独特的神经递质作用形式被描述 这不是由发射器引起的膜的打开引起的 频道 相反，它是由发射机对信号的调制引起的。 通过电压打开通道。 这种形式的神经递质的作用 首先涉及到正性肌力和变时作用， 去甲肾上腺素对心肌的影响 从那时起，神经递质 电压依赖性通道的调节已经描述了许多 组织中 特别是，这种类型的发射器效应可能涉及到 脊髓中感觉神经传递的突触前抑制。 本研究拟在鸡胚感觉神经系统中探讨这一现象。 在体内和体外的神经元。 具体来说， 神经递质（例如，GABA和去甲肾上腺素）减少 神经元胞体中的电压依赖性Ca电流将被 研究使用电压钳和单通道记录技术。 这些实验旨在测试环核苷酸的参与 和细胞内钙离子在通道调节中的作用， 它们在调节感觉神经递质释放中的作用 神经元 关于突触前神经元突触后传导机制的假说的检验 抑制也将在半切脊髓中进行 制备和鉴定的感觉神经元和脊髓神经元之间的突触 脐带细胞在培养基中一起生长。 这些研究将利用 观察到两种不同的和功能不同的GABA 受体存在于鸡胚感觉神经元上。 特异性激动剂 对于这些受体，将允许区分两种建议的 脊髓突触前抑制假说。

In recent years a unique form of neurotransmitter action has been described which does not result from a transmitter-induced opening of a membrane channel. Rather, it results from a modulation by the transmitter of a channel opened by voltage. A role for this form of neurotransmitter action was first implicated in the positive inotropic and chronotropic effects of nor-adrenaline on cardiac muscle. Since that time, neurotransmitter modulation of voltage-dependent channels has been described for many tissues. In particular, this type of transmitter effect may be involved in presynaptic inhibition of sensory neurotransmission in the spinal cord. This proposal investigates this phenomenon in embryonic chick sensory neurons in vivo and in vitro. Specifically, the mechanism by which neurotransmitters (e.g., GABA and nor-epinephrine) decrease the voltage-dependant Ca current in the cell bodies of the neurons will be investigated using voltage clamp and single channel recording techniques. The experiments are designed to test the involvement of cyclic nucleotides and intracellular Ca in channel modulation and to gain information about their roles in the regulation of neurotransmitter release from sensory neurons. Tests of hypotheses concerning the mechanism of pre-synaptic inhibition will also be performed both in hemisected spinal cord preparations and at identified synapses between sensory neurons and spinal cord cells grown together in culture. These studies will make use of the observation that two pharmacologically and functionally distinct GABA receptors exist on embryonic chick sensory neurons. The specific agonists for these receptors will allow a discrimination between two proposed hypotheses for presynaptic inhibition in the spinal cord.