Ghoneim M M, El-Zahaby H M, Block R I
Department of Anesthesia, University of Iowa, Iowa City 52242-1079, USA.
Pharmacol Biochem Behav. 1999 Mar;62(3):449-55. doi: 10.1016/s0091-3057(98)00196-8.
Classical conditioning of the rabbit nictitating membrane response (NMR) was accomplished by presenting a 75-ms tone conditioned stimulus (CS) at intervals of 0, 100, 200, 400, and 800 ms before the presentation of a 100-ms shock unconditioned stimulus. Following every four paired trials (tone followed by shock), the occurrence of conditioned responses (CRs) was tested on every fifth trial in which only tone was presented (test trials). Three doses of nitrous oxide in oxygen (0, 33, and 67%) were used during conditioning. Nitrous oxide produced dose-dependent decrements of learning. Conditioned responding was related to the interstimulus interval (ISI) by a concave-down function. The higher dose of nitrous oxide caused more decrements of learning at several ISIs compared to the other two doses, changing the shape of the curve. Trace conditioning, which was examined in the present study, was more impaired under the influence of nitrous oxide than conditioning in a previous study, which used the standard delay paradigm. Thus, the drug impairs explicit memory more than implicit memory.
通过在100毫秒的电击非条件刺激出现前，以0、100、200、400和800毫秒的间隔呈现75毫秒的音调条件刺激（CS），实现了兔瞬膜反应（NMR）的经典条件反射。每进行四次配对试验（音调后接电击）后，在每五次仅呈现音调的试验（测试试验）中测试条件反应（CRs）的发生情况。在条件反射过程中使用了三种一氧化二氮在氧气中的浓度（0%、33%和67%）。一氧化二氮产生了剂量依赖性的学习减退。条件反应与刺激间隔（ISI）呈向下凹陷的函数关系。与其他两种剂量相比，较高剂量的一氧化二氮在几个ISI下导致更多的学习减退，改变了曲线的形状。本研究中所考察的痕迹条件反射，在一氧化二氮的影响下比先前一项使用标准延迟范式的研究中的条件反射受到的损害更大。因此，该药物对显性记忆的损害大于隐性记忆。
