Xu X
Department of Psychology, Grand Valley State University, Allendale, Michigan 49401, USA.
Pharmacol Biochem Behav. 1997 Oct;58(2):491-6. doi: 10.1016/s0091-3057(97)00283-9.
Previous experiments have shown that administration of intracranial MK-801 blocks learning of classical fear conditioning in goldfish. The impairment of learning was decreased when fish received limited pretraining, suggesting that only the early phase of conditioning may be sensitive to disruption by MK-801. The present studies investigated the possibility that classical conditioning in goldfish consists of two successive phases and that only the initial phase depends critically on N-methyl-D-aspartate receptor function. A series of experiments showed that the anterograde amnestic effect of MK-801 is decreased or eliminated when fish received pretraining consisting of 6 or 12 conditioning trials, respectively. MK-801-sensitive learning is inferred to be completed within 12 trials. The neural mechanism of the learning which occurs during the later trials is manifestly insensitive of MK-801. Furthermore, MK-801 impaired learning when fish received pretraining consisting of six pseudoconditioning trials. The results indicate that MK-801-sensitive learning is associative or depends on the contiguity of the conditioned stimulus (CS) and unconditioned stimulus (US) and that MK-801 selectively impairs learning of the CS-US contiguity.
先前的实验表明，向金鱼颅内注射MK-801会阻碍经典恐惧条件反射的学习。当金鱼接受有限的预训练时，学习障碍会减轻，这表明只有条件反射的早期阶段可能对MK-801的干扰敏感。本研究探讨了金鱼的经典条件反射是否由两个连续阶段组成，以及是否只有初始阶段关键依赖于N-甲基-D-天冬氨酸受体功能的可能性。一系列实验表明，当金鱼分别接受由6次或12次条件反射试验组成的预训练时，MK-801的顺行性遗忘效应会降低或消除。推断MK-801敏感的学习在12次试验内完成。后期试验中发生的学习的神经机制显然对MK-801不敏感。此外，当金鱼接受由6次伪条件反射试验组成的预训练时，MK-801会损害学习。结果表明，MK-801敏感的学习是联想性的或依赖于条件刺激（CS）和无条件刺激（US）的接近性，并且MK-801选择性地损害CS-US接近性的学习。
