Gruner W, Silva L R
Department of Physiology, Tufts University School of Medicine, Boston, Massachusetts 02111.
J Neurosci. 1994 May;14(5 Pt 1):2800-8. doi: 10.1523/JNEUROSCI.14-05-02800.1994.
Synaptic transmission between embryonic chick dorsal root ganglion (DRG) neurons and spinal cord neurons was studied in dissociated cell culture. Stimulation of DRG neurons evoked monosynaptic and polysynaptic excitatory responses in the spinal neurons. These responses could be reversibly blocked by application of 6-cyano-7-nitroquinoxaline-2,3-dione (a selective non-NMDA receptor antagonist) and irreversibly eliminated through the presynaptic action of omega-conotoxin GVIA (a selective N-type calcium channel antagonist). As N-type calcium channels in DRG neuron somata are targets for modulation via GABAB receptors, we tested the role of these receptors as regulators of synaptic transmission. Baclofen (a selective GABAB receptor agonist) reversibly inhibited synaptic transmission via a presynaptic, pertussis toxin-sensitive mechanism; CGP 35348 (a selective GABAB receptor antagonist) blocked the actions of baclofen. Taken together, these results demonstrate that N-type calcium channels play a dominant role in glutamatergic sensory neurotransmission. They suggest, in addition, that modulation of N-channel activity may underlie, at least in part, presynaptic inhibition of synaptic transmission between DRG neurons and their targets in the intact spinal cord.
在解离细胞培养中研究了胚胎鸡背根神经节（DRG）神经元与脊髓神经元之间的突触传递。刺激DRG神经元可在脊髓神经元中诱发单突触和多突触兴奋性反应。应用6-氰基-7-硝基喹喔啉-2,3-二酮（一种选择性非NMDA受体拮抗剂）可使这些反应可逆性阻断，而通过ω-芋螺毒素GVIA（一种选择性N型钙通道拮抗剂）的突触前作用可不可逆地消除这些反应。由于DRG神经元胞体中的N型钙通道是通过GABAB受体进行调节的靶点，我们测试了这些受体作为突触传递调节因子的作用。巴氯芬（一种选择性GABAB受体激动剂）通过一种对百日咳毒素敏感的突触前机制可逆性抑制突触传递；CGP 35348（一种选择性GABAB受体拮抗剂）可阻断巴氯芬的作用。综上所述，这些结果表明N型钙通道在谷氨酸能感觉神经传递中起主导作用。此外，它们还表明，N通道活性的调节可能至少部分地是完整脊髓中DRG神经元与其靶标之间突触传递的突触前抑制的基础。
