Reconsolidation of a long-term spatial memory is impaired by cycloheximide when reactivated with a contextual latent learning trial in male and female rats.

Reconsolidation of long-term memory has become a topic of great interest in recent years, and has the potential to provide important information regarding memory processes and the treatment of memory-related disorders. The present study examined the role of systemic protein synthesis inhibition in reconsolidation of a long-term spatial memory reactivated by a contextual latent learning trial in male and female rats. Using the Morris water maze, we demonstrate that: 1) a contextual latent reactivation treatment enhances memory, 2) systemic protein synthesis inhibition selectively impairs test performance when administered in conjunction with a memory reactivation treatment, and 3) that these effects are more pronounced in female rats. These findings indicate a role for protein synthesis in the reconsolidation of a contextually reactivated long-term spatial memory using the water maze, and a potential differential effect of sex in this apparatus. The role of the strength of the memory trace is discussed and the relevance of these findings to theories of reconsolidation and therapeutic treatment of post-traumatic stress disorder is discussed.

Anterior rhinal cortex and amygdala: dissociation of their contributions to memory and food preference in rhesus monkeys.

Rhesus monkeys were trained on 2 versions of delayed nonmatching-to-sample, one with multiple pairs of objects and the other with a single pair, to evaluate their ability to remember objects. They then received either bilateral aspiration lesions of the anterior rhinal cortex or bilateral excitotoxic lesions of the amygdala, or were retained as unoperated controls. On re-presentation of the multiple-pair task, monkeys with anterior rhinal cortex lesions failed to show the improvement observed in both other groups in remembering the objects over delay intervals ranging from 10 to 60 s. Also, monkeys with anterior rhinal cortex lesions were impaired relative to the controls in relearning the single-pair version of the task. Conversely, on a formal test of food preference, monkeys with amygdala lesions showed abnormal patterns of food choice, whereas monkeys with anterior rhinal cortex lesions did not. Visual memory impairments formerly attributed to amygdala damage are probably due to the rhinal cortex damage associated with aspiration lesions of the amygdala.

MK-801 induced retrieval, but not acquisition, deficits for passive avoidance conditioning.

Two experiments using a state-dependent retention (SDR) design determined whether MK-801 blocked the acquisition and retention of an avoidance response. In Experiments 1 and 2, rats were trained and tested 30 min after injections of either saline or MK-801 (0.05 and 0.10 mg/kg, respectively). Two minutes after training, subjects were immediately tested, and in both experiments, the avoidance response was acquired. The 24-h retention tests for Experiment 1 revealed that the data marginally supported a SDR interpretation. In Experiment 2, the dose of MK-801 was increased to 0.10 mg/kg, and the results showed that MK-801 rendered passive avoidance (PA) state-dependent. These experiments indicate that neither the 0.05 nor 0.10 mg/kg doses of MK-801 prevented acquisition of the avoidance response and that the latter dose rendered memory for PA training state-dependent. It is suggested that doses of MK-801 that did not impair PA learning can function as a cue state and influence expression of memory for PA.

Pretest administration of glucose attenuates infantile amnesia for passive avoidance conditioning in rats.

Infantile amnesia in rats may be attenuated by a wide variety of retrieval cues which reactivate memory for the training episode. The present study investigated the effects of glucose on memory retrieval in infant rats. In Experiment 1, 17-day-old preweanling rats were trained to criterion on passive avoidance conditioning. Twenty-four hours later, each subject received a subcutaneous injection of either saline, 100 mg/kg, or 250 mg/kg of glucose just prior to testing. Saline animals displayed poor retention scores, suggesting infantile amnesia; however, glucose significantly attenuated the 24-hr retention loss. Experiment 2 attempted to replicate the previous experiment, control for age and general drug effects, and extend the dose of glucose to 400 mg/kg. The results of Experiment 2 were consistent with Experiment 1 and also indicated that infant subjects performed significantly worse than adults. Both 100 and 250 mg/kg of glucose significantly attenuated infantile amnesia; however, 400 mg/kg had no effect. These results support a retrieval failure view of infantile amnesia and extend the memory-influencing properties of glucose to infants. Context and neuroendocrine views of memory retrieval are discussed.

Differential effects of glucose on modulation of emotional and nonemotional spatial memory tasks.

Research examining the memory-enhancing effects of glucose in humans has been limited to mnemonic tasks lacking affective components, even though glucose may be a mechanism for emotion-induced memory enhancement. This limitation does not permit analysis of interactions between the enhancing properties of emotional stimuli and glucose. Participants were administered either glucose or saccharin 15 min prior to completing a neutral or emotional spatial memory task. Performance under three glycemic conditions (100 mg/kg or 50 g glucose, or placebo) for the two sets of emotional stimuli revealed a significant interaction. Both 100-mg/kg and 50-g doses of glucose resulted in impaired performance for emotional stimuli. For neutral stimuli, a 100-mg/kg dose enhanced memory, whereas a 50-g dose showed no effect. Results indicate that the enhancing effects of emotional stimuli may be attenuated by the consumption of glucose and suggest that recent food consumption should be considered in paradigms examining memory.

The application of trace element analysis by X-ray fluorescence to human blood serum.

The need for a simple, yet fast and accurate method for trace element analysis of human tissues is remarded on. Such a method is the use of x-ray fluorescence in conjunction with one of the new generation of solid-state x-ray detectors. The method is described, together with an example of its application-apilot study of forty-two blood serum samples supplied by the Manitoba Cancer Research Institute.

Post-training glucose administration attenuates forgetting of passive-avoidance conditioning in 18-day-old rats.

The study of memory modulation in infant rats has typically focused on reminder/retrieval treatments involving reexposure to components of the internal or external training context. Rarely have studies employed pharmacological treatments to investigate the neurochemical substrates of memory storage in preweanling rats. The present study investigated the effect of 100 mg/kg of glucose, a common memory modulator in adult mammals, on memory for passive-avoidance conditioning in 18-day-old Sprague-Dawley rats. Subjects that were administered an immediate post-training injection of glucose performed significantly better, on a retention test 24 h following training, than those animals that received saline. The glucose group also performed comparably to a control group that was tested 10 min following training. These results are consistent with those of the memory modulation literature in adults and suggest that the rapid rate of forgetting in immature organisms may be the result of a deficiency in a general memory modulatory system.