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C Messier

Publications and source records attributed to C Messier.

41 records · Page 3Linked to original sources
PubMed1988

Effects of adrenal demedullation on the conditioned emotional response and on the memory improving action of glucose.

Results of previous experiments have demonstrated that posttraining, noncontingent ingestion of sucrose solutions, or injection of glucose solutions improve retention of various learning tasks. In the present experiment, we tested the hypothesis that this effect is due to a glucose-stimulated release of epinephrine from the adrenal medulla by testing the effect of posttraining glucose injections on retention of a conditioned emotional response (CER) in demedullated rats. In a preliminary experiment, demedullated rats were found to be deficient at acquiring the CER, but a similar deficit in sham-operated animals suggested that this was due to the surgical procedure rather than to the absence of the adrenal medulla. When appropriate shock parameters were used, posttraining glucose improved retention of the CER in a manner parallel to the effect of this treatment in normal rats. It was concluded that the memory improving effect of posttraining glucose does not involve an effect of this substance on the adrenal medulla.

Adrenal Medulla↗
PubMed1987

Memory improvement by glucose, fructose, and two glucose analogs: a possible effect on peripheral glucose transport.

The memory-improving action of post-training, noncontingent injections of glucose was investigated in a series of experiments which examined the effects of several substances that interact with glucose metabolism on the retention of a conditioned emotional response and on blood glucose levels in male hooded rats. Although post-training glucose injections of 1, 2, and 3 g/kg all produced similar increases in blood glucose, only 2 g/kg improved retention, suggesting that attainment of a particular blood glucose level is not critical for memory improvement. Post-training injections of a range of insulin doses (0.25-4 IU/kg) failed to affect retention. Post-training injection of fructose (the same doses as were used for glucose) had no effect on blood glucose levels and, as with glucose, only the 2 g/kg dose improved retention. This finding suggests that blood glucose levels are not critical for the memory-improving effect, that glucose and fructose may act on the same substrate and, because fructose does not act directly on the brain, it raises the possibility that both substances act peripherally. Post-training injections of 2-deoxyglucose and 3-O-methylglucose both improved retention. The fact that these mostly nonmetabolized glucose analogs were effective suggests that the memory-improving action of glucose may depend on the activation of a membrane glucose transport mechanism. The implications of the possible action of glucose on peripheral transport mechanisms for understanding the effect of reinforcers on memory are discussed.

3-O-Methylglucose↗
PubMed1984

Contingent and non-contingent actions of sucrose and saccharin reinforcers: effects on taste preference and memory.

Preference curves were generated by comparing 14 concentrations each of sucrose and saccharin in a 20-minute test in which rats were presented with a choice of a sweet solution and water. The most preferred concentration and one concentration above and one below the most preferred for both substances were studied further. The sucrose and saccharin solutions were contingently paired with novel flavors in a conditioned taste preference (CTP) paradigm. All of the sweet solutions enhanced the animals' subsequent conditioned taste preferences for the flavors. The lack of difference between the effects of the solutions in this paradigm suggest that they had similar rewarding values and that CTP's are established mainly on the basis of taste cues. In another experiment, post-training ingestion of sucrose solutions, injection of glucose and, to a much lesser extent, ingestion of saccharin solutions retroactively and non- contingently improved retention of a previously formed, classically conditioned association. The results indicated that this effect was mainly due to the post- ingestional effects of the sucrose solutions, although taste factors also had a slight influence. This series of experiments parallels previous findings with self-stimulation as the reinforcer. The results support the hypothesis that reinforcers have a dual action on behavior: the elicitation of affective states that, when paired with environmental stimuli, can influence future behavior towards those stimuli; and a non-contingent retroactive enhancement of retention of previously formed associations.

Animals↗
PubMedDate not supplied

Effect of glucose and peripheral glucose regulation on memory in the elderly.

We examined changes in cognitive performance following the intake of a glucose (50 g) or saccharin solution (50 mg) in fasted elderly male and female subjects. Glucoregulation was estimated using a recovery index that was used to categorize subjects within each sex as having poor or good recovery. Elderly males with poor recovery performed worse on the Logical Memory subtest of the Wechsler Memory Scale and on the free recall or recognition parts of a work list task. The item analysis of the Logical Memory subtest showed that male subjects with poor recovery remembered less of the last items of the paragraphs after drinking saccharin while the first items were equally remembered by both groups. Glucose improved the performance of the males with good regulation for the first seven items while the performance of males with poor regulation decreased for those items under glucose. The present study support the notion that peripheral glucoregulation can influence memory performance and that the ingestion of glucose can influence certain aspects of memory functioning.

Aged↗