Brown E R, Piscopo S, Chun J-T, Francone M, Mirabile I, D'Aniello A
Neurobiology Laboratory, Stazione Zoologica Anton Dohrn, Naples, Italy.
Amino Acids. 2007 Jan;32(1):53-7. doi: 10.1007/s00726-006-0349-3. Epub 2006 Jun 1.
L- and D-aspartic acids (L-Asp and D-Asp) are present in the majority of nervous systems. In phylogeny, significant levels have been reported in mollusc brains, particularly cephalopods. To examine the role of L- and D-Asp on a cephalopod receptor, we studied ligand gating of a squid glutamate receptor (SqGluR) expressed in HEK 239 (human embryonic kidney) cells. Under voltage clamp, application of L-glutamate (L-Glu; 1-30 mM), but not D-glutamate (D-Glu), or L- or D-Asp, evoked an inward current of 0.1 nA. L- or D-Asp (200 microM) applied with 20 mM L-Glu, slowed the time course of activation and inactivation of the L-Glu gated current (time constant increased from 1 s (L-Glu alone) to 3 s (D-Asp and L-Glu) and to 19 s (L-Asp and L-Glu)). Our results suggest that in molluscan systems, aspartic acid could act as a neuromodulator during glutamatergic transmission and could significantly alter synaptic integration by slowing glutamate receptor gating.
L-天冬氨酸和D-天冬氨酸（L-Asp和D-Asp）存在于大多数神经系统中。在系统发育过程中，据报道在软体动物大脑，尤其是头足类动物的大脑中含量显著。为了研究L-天冬氨酸和D-天冬氨酸在头足类动物受体上的作用，我们研究了在HEK 293（人胚肾）细胞中表达的鱿鱼谷氨酸受体（SqGluR）的配体门控。在电压钳制下，施加L-谷氨酸（L-Glu；1-30 mM），而不是D-谷氨酸（D-Glu）或L-或D-天冬氨酸，会诱发0.1 nA的内向电流。将L-或D-天冬氨酸（200 μM）与20 mM L-谷氨酸一起施加，会减慢L-谷氨酸门控电流的激活和失活时间进程（时间常数从1秒（单独使用L-谷氨酸）增加到3秒（D-天冬氨酸和L-谷氨酸）和19秒（L-天冬氨酸和L-谷氨酸））。我们的结果表明，在软体动物系统中，天冬氨酸在谷氨酸能传递过程中可能作为一种神经调节剂，并可能通过减慢谷氨酸受体门控来显著改变突触整合。
