Collins G G, Anson J, Probett G A
Brain Res. 1981 Jan 5;204(1):103-20. doi: 10.1016/0006-8993(81)90655-7.
A study has been made of the effects of depolarizing stimuli on the release of endogenous amino acid neurotransmitter candidates (aspartate, glutamate, GABA and taurine) from in vitro preparations of rat and guinea pig olfactory cortex. Exposure of small cubes of olfactory cortex tissue from either species to potassium chloride (50 mM) was accompanied by a calcium-dependent release of aspartate, glutamate and GABA. A similar release pattern was evoked by protoveratrine A (100 muM) although the release was largely calcium-independent. Neither agent led to increased release of taurine. Electrical stimulation of the excitatory input (lateral olfactory tract) of freshly prepared, synaptically intact olfactory cortex slices of both species induced significant release of aspartate and GABA from the uncut pial surface and of aspartate, GABA and glutamate from the cut surface. Evoked taurine release occurred from both surfaces of rat olfactory cortex slices but no release was detected from guinea pig olfactory cortex slices. These patterns of release were unaffected by changes in stimulus frequency and were mimicked by protoveratrine A (100 muM) applied to one or other surface. Preincubation of slices from rats for 2 led to loss of tissue amino acids and to changes in their release patterns; the presence of glutamine (5 mM) during preincubation prevented the loss of amino acids but did not alter their pattern of release. Because of the close similarities between both the electrophysiological properties and the patterns of amino acid release it is concluded that there is probably an identity of amino acid neurotransmitters (aspartate, glutamate and GABA) in rat and guinea pig olfactory cortex. The role of taurine in the rat olfactory cortex is unknown but would seem unlikely to be that of a neurotransmitter. The results are discussed: (i) in terms of the cellular origins of the released amino acids; and (ii) wit respect to apparent experimental discrepancies which have appeared in the literature.
一项关于去极化刺激对大鼠和豚鼠嗅皮质体外制剂中内源性氨基酸神经递质候选物（天冬氨酸、谷氨酸、γ-氨基丁酸和牛磺酸）释放影响的研究。将来自任一物种的小块嗅皮质组织暴露于氯化钾（50 mM）时，伴随着天冬氨酸、谷氨酸和γ-氨基丁酸的钙依赖性释放。原藜芦碱A（100 μM）也引发了类似的释放模式，尽管这种释放很大程度上不依赖于钙。两种药剂均未导致牛磺酸释放增加。对两个物种新鲜制备的、突触完整的嗅皮质切片的兴奋性输入（外侧嗅束）进行电刺激，诱导未切开的软脑膜表面显著释放天冬氨酸和γ-氨基丁酸，切开表面显著释放天冬氨酸、γ-氨基丁酸和谷氨酸。大鼠嗅皮质切片的两个表面均出现诱发的牛磺酸释放，但豚鼠嗅皮质切片未检测到释放。这些释放模式不受刺激频率变化的影响，并且可被应用于一个或另一个表面的原藜芦碱A（100 μM）模拟。将大鼠切片预孵育2小时导致组织氨基酸损失并改变其释放模式；预孵育期间存在谷氨酰胺（5 mM）可防止氨基酸损失，但未改变其释放模式。由于电生理特性和氨基酸释放模式之间存在密切相似性，得出结论：大鼠和豚鼠嗅皮质中可能存在相同的氨基酸神经递质（天冬氨酸、谷氨酸和γ-氨基丁酸）。牛磺酸在大鼠嗅皮质中的作用尚不清楚，但似乎不太可能是神经递质的作用。对结果进行了讨论：（i）从释放的氨基酸的细胞来源方面；（ii）关于文献中出现的明显实验差异。
