Bradley R M, King M S, Wang L, Shu X
University of Michigan, Ann Arbor 48109, USA.
Chem Senses. 1996 Jun;21(3):377-85. doi: 10.1093/chemse/21.3.377.
The rostral nucleus of the solitary tract (rNST) is the first central relay in the gustatory pathway. While previous investigations have provided a wealth of information on the pattern of central terminations of gustatory afferent fibers, the morphology of synaptic connections of rNST neurons and responses of second order neurons to taste stimuli applied to the tongue, little is known regarding the neurophysiological characteristics of synaptic transmission in rNST. We have used an in vitro brain slice preparation of the rNST to study the intrinsic biophysical properties, neuropharmacology and synaptic responses of rNST neurons. These experiments have revealed that rNST neurons respond to the excitatory amino acid neurotransmitter glutamate, as well as the inhibitory amino acid neurotransmitter gamma amino butyric acid (GABA). By use of glutamate receptor agonists and antagonists we have shown that rNST neurons have AMPA/kainate and NMDA ionotropic glutamate receptors, as well as matabotropic glutamate receptors. In addition, rNST neurons respond to both GABAA and GABAB receptor agonists. The nature of the transmission at the synapse between primary afferent fibers and second order neurons in rNST has been examined by electrical stimulation of the solitary tract to elicit post-synaptic potentials (PSP). Three types of monosynaptic PSP result from stimulation of the solitary tract: excitatory post-synaptic potentials, inhibitory post-synaptic potentials, and a complex mixture of excitatory and inhibitory potentials. These new discoveries provide details about synaptic transmission in rNST and thereby clarify the underlying mechanism by which gustatory information is processed.
孤束吻侧核（rNST）是味觉通路中的首个中枢中继站。尽管先前的研究已提供了大量有关味觉传入纤维中枢终末模式、rNST神经元突触连接形态以及二级神经元对施加于舌部的味觉刺激反应的信息，但对于rNST中突触传递的神经生理学特征却知之甚少。我们使用rNST的体外脑片制备来研究rNST神经元的内在生物物理特性、神经药理学和突触反应。这些实验表明，rNST神经元对兴奋性氨基酸神经递质谷氨酸以及抑制性氨基酸神经递质γ-氨基丁酸（GABA）均有反应。通过使用谷氨酸受体激动剂和拮抗剂，我们发现rNST神经元具有AMPA/海人藻酸离子型谷氨酸受体、NMDA离子型谷氨酸受体以及代谢型谷氨酸受体。此外，rNST神经元对GABAA和GABAB受体激动剂均有反应。通过电刺激孤束以引发突触后电位（PSP），研究了rNST中初级传入纤维与二级神经元之间突触传递的性质。刺激孤束会产生三种类型的单突触PSP：兴奋性突触后电位、抑制性突触后电位以及兴奋性和抑制性电位的复杂混合。这些新发现提供了有关rNST中突触传递的详细信息，从而阐明了味觉信息处理的潜在机制。
