Kamishita T, Haruta H, Torii N, Tsumoto T, Hicks T P
Department of Neurophysiology, Biomedical Research Centre, Osaka University Medical School, Japan.
Can J Physiol Pharmacol. 1995 Sep;73(9):1312-22. doi: 10.1139/y95-186.
Two forms of use-dependent synaptic plasticity, called long-term potentiation (LTP) and long-term depression (LTD), can be elicited in the visual cortex following different paradigms of electrophysiological stimulation. These neurobiological phenomena often are considered as necessary components of models for the alteration in function of the nervous system that must occur at some level for the establishment and (or) maintenance of memory engrams, for learning processes, or for the consolidation of active neural connections and regression of inactive contacts in the developing brain. It has been postulated that for LTP and LTD to be produced in the hippocampus, activation of a particular subtype of excitatory amino acid receptor, the metabotropic receptor, is a critical requirement. Only recently has it become possible to test this hypothesis directly, as a new compound, (+/-)-alpha-methyl-4-carboxyphenylglycine (MCPG), has been introduced and the suggestion made that it selectively antagonizes the metabotropic receptor. This substance has been tested in the present study on responses recorded from slices of rat visual cortex and has been found both to block the activation of the metabotropic receptor and to interfere selectively with the form of synaptic plasticity called LTD. It thus appears from the experiments reported in this paper as though the metabotropic receptor subtype that is blocked by MCPG is required for the expression of LTD but not for the expression of LTP, in the visual cortex of adult rats.
在电生理刺激的不同范式之后，视觉皮层中可引发两种形式的使用依赖性突触可塑性，即长时程增强（LTP）和长时程抑制（LTD）。这些神经生物学现象通常被视为神经系统功能改变模型的必要组成部分，而这种改变在某种程度上必然会发生，以建立和（或）维持记忆痕迹、进行学习过程，或在发育中的大脑中巩固活跃的神经连接并使不活跃的突触联系消退。据推测，要在海马体中产生LTP和LTD，一种特定亚型的兴奋性氨基酸受体，即代谢型受体的激活是关键要求。直到最近，随着一种新化合物（±）-α-甲基-4-羧基苯甘氨酸（MCPG）的引入，并有人提出它能选择性拮抗代谢型受体，才使得直接检验这一假设成为可能。在本研究中，已对从大鼠视觉皮层切片记录的反应进行了该物质的测试，结果发现它既能阻断代谢型受体的激活，又能选择性地干扰被称为LTD的突触可塑性形式。因此，从本文报道的实验来看，在成年大鼠的视觉皮层中，被MCPG阻断的代谢型受体亚型对于LTD的表达是必需的，但对于LTP的表达则不是必需的。
