Houpt T A, Berlin R
Department of Psychiatry, Cornell University Medical College, White Plains, New York 10605, USA.
Learn Mem. 1999 Jan-Feb;6(1):37-46.
Short-term memory is a rapid, labile, and protein-synthesis-independent phase of memory. The existence of short-term memory in conditioned taste aversion (CTA) learning has not been demonstrated formally. To determine the earliest time at which a CTA is expressed, we measured intraoral intake of sucrose at 15 min, 1 hr, 6 hr, or 48 h after contingent pairing of an intraoral infusion of 5% sucrose (6.6 ml over 6 min) and toxic lithium chloride injection (76 mg/kg). Rats were implanted with intraoral catheters to allow presentation of taste solutions at arbitrary times. Intraoral intake was measured under conditions of long-delay, single-trial learning typical of CTA. Rats decreased intraoral intake of sucrose at 15 min after contingent pairing of sucrose and LiCl, but not after noncontingent LiCl or sucrose. Thus CTA learning can be expressed rapidly. To determine if short-term CTA memory is labile and decays in the absence of long-term memory, we measured intraoral intake of sucrose after pairing sucrose with low doses of LiCl. Rats received an intraoral infusion of 5% sucrose (6 ml/6 min); 30 min later LiCl was injected at three different doses (19, 38, or 76 mg/kg). A second intraoral infusion of sucrose was administered 15 min, 1 hr, 3 hr, 4.5 hr, 6 hr, or 48 hr later. The formation of long-term CTA memory was dependent on the dose of LiCl paired with sucrose during acquisition. Low doses of LiCl induced a CTA that decayed within 6 hr after pairing. Central administration of the protein synthesis inhibitor cycloheximide prior to LiCl injection blocked long-term CTA expression at 6 and 48 hr, but not short-term CTA expression at 1 hr. Thus, short-term memory for CTA learning exists that is acquired rapidly and independent of protein synthesis, but labile in the absence of long-term memory formation.
短期记忆是记忆的一个快速、不稳定且不依赖蛋白质合成的阶段。条件性味觉厌恶（CTA）学习中短期记忆的存在尚未得到正式证实。为了确定CTA最早表达的时间，我们在口腔内注入5%蔗糖（6分钟内注入6.6毫升）与注射有毒的氯化锂（76毫克/千克）进行配对后15分钟、1小时、6小时或48小时，测量了蔗糖的口腔内摄入量。给大鼠植入口腔内导管，以便在任意时间呈现味觉溶液。在典型的CTA长期延迟、单次试验学习条件下测量口腔内摄入量。在蔗糖和氯化锂配对后15分钟，大鼠口腔内蔗糖摄入量减少，但在非配对的氯化锂或蔗糖处理后未减少。因此，CTA学习可以快速表达。为了确定短期CTA记忆是否不稳定且在没有长期记忆的情况下会衰退，我们在蔗糖与低剂量氯化锂配对后测量了蔗糖的口腔内摄入量。大鼠接受口腔内注入5%蔗糖（6毫升/6分钟）；30分钟后，以三种不同剂量（19、38或76毫克/千克）注射氯化锂。在15分钟、1小时、3小时、4.5小时、6小时或48小时后进行第二次口腔内蔗糖注入。长期CTA记忆的形成取决于获取过程中与蔗糖配对的氯化锂剂量。低剂量的氯化锂诱导的CTA在配对后6小时内衰退。在注射氯化锂之前中枢给予蛋白质合成抑制剂环己酰亚胺可阻断6小时和48小时的长期CTA表达，但不阻断1小时时的短期CTA表达。因此，CTA学习存在快速获得且不依赖蛋白质合成的短期记忆，但在没有长期记忆形成的情况下不稳定。
