Do K Q, Binns K E, Salt T E
Brain Research Institute, University of Zurich, Switzerland.
Neuroscience. 1994 Jun;60(3):581-6. doi: 10.1016/0306-4522(94)90488-x.
The neurophysiology and neuroanatomy of the thalamus have been extensively studied in a variety of species and sensory systems. The identity of the neurotransmitter(s) which mediate the excitation from ascending sensory afferents on to thalamic relay neurons is, however, still unclear, although it appears to be a substance which is a ligand for excitatory amino acid receptors, as the responses of ventrobasal thalamus neurons to natural stimulation of somatosensory afferents arising from the mustachial vibrissae of the rat are mediated by ionotropic excitatory amino acid receptors, when stimulation is performed using an air-jet directed at the vibrissa receptor field. In an effort to determine the transmitter of these sensory afferents, we have attempted to detect the release of amino acids in the ventrobasal thalamus in vivo upon such stimuli. We have thus used a similar natural stimulation protocol, together with push-pull perfusion and recording in the ventrobasal thalamus, and we describe the release of the amino acid, arginine, in this brain area following physiological stimulation of afferents. Furthermore, we show that application of L-arginine on to thalamic relay neurons can facilitate sensory synaptic transmission, possibly via the synthesis of the diffusable messenger, free radical gas, nitric oxide. This may represent a novel, local positive-feedback, modulatory system which could enhance the responsiveness of thalamic neurons to sensory input.
丘脑的神经生理学和神经解剖学已在多种物种和感觉系统中得到广泛研究。然而，介导来自上行感觉传入神经对丘脑中继神经元的兴奋作用的神经递质的身份仍不清楚，尽管它似乎是一种作为兴奋性氨基酸受体配体的物质，因为当使用指向触须感受野的喷气进行刺激时，大鼠触须的体感传入神经对丘脑腹侧基底核神经元的自然刺激反应是由离子型兴奋性氨基酸受体介导的。为了确定这些感觉传入神经的递质，我们试图检测在这种刺激下体内丘脑腹侧基底核中氨基酸的释放。因此，我们使用了类似的自然刺激方案，结合推挽灌注和丘脑腹侧基底核记录，并描述了在传入神经受到生理刺激后该脑区氨基酸精氨酸的释放。此外，我们表明，将L-精氨酸应用于丘脑中继神经元可以促进感觉突触传递，可能是通过可扩散信使自由基气体一氧化氮的合成。这可能代表一种新的局部正反馈调节系统，它可以增强丘脑神经元对感觉输入的反应性。
