Wu Eric
Neuroscience Program, Department of Physiology and Biophysics, University of Miami School of Medicine, 1600 NW 10th Avenue, Miami, FL 33136, USA.
Invert Neurosci. 2002 Apr;4(3):157-64. doi: 10.1007/s10158-002-0017-6. Epub 2002 Apr 12.
The N-methyl- D-aspartate (NMDA) receptor, able to detect the coincidence of pre- and postsynaptic events, is considered to be the molecular analogue of associative learning. Associative learning is well known in leeches, particularly for reflexive shortening. The neuronal circuits underlying shortening have been documented and include neurons that release glutamate. Is this type of learning in leeches also mediated by NMDA receptors? The synapse between the P sensory neuron and the motoneuron-like AP cell was examined and: (1) NMDA failed to elicit a response in the AP cell, (2) the NMDA receptor antagonist 2-amino-5-phosphopentanoic acid affected synaptic transmission only at high, non-specific levels, and (3) the antagonist for the glycine-binding site 7-chloro-kynurenic acid at 20 microM did not inhibit transmission. Therefore, there are evidently no NMDA receptors at the P to AP synapse, suggesting other mechanisms of associative learning in leeches.
N-甲基-D-天冬氨酸（NMDA）受体能够检测突触前和突触后事件的同时发生，被认为是联想学习的分子类似物。联想学习在水蛭中是众所周知的，特别是对于反射性缩短。已经记录了缩短背后的神经回路，包括释放谷氨酸的神经元。水蛭中的这种学习类型是否也由NMDA受体介导？研究了P感觉神经元和运动神经元样AP细胞之间的突触，结果如下：（1）NMDA未能在AP细胞中引发反应；（2）NMDA受体拮抗剂2-氨基-5-磷酸戊酸仅在高浓度、非特异性水平上影响突触传递；（3）20微摩尔的甘氨酸结合位点拮抗剂7-氯犬尿氨酸不抑制传递。因此，在P到AP突触处显然没有NMDA受体，这表明水蛭中存在其他联想学习机制。
