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At least 307 records · Page 17Linked to original sources
PubMed2005

Effects of active shock avoidance learning on hippocampal neurogenesis and plasma levels of corticosterone.

Hippocampal granule neurons that are newly formed during adulthood might be involved in learning and memory processes. Experimental data suggest that only hippocampus-dependent learning tasks stimulate neurogenesis. To further address this issue, the effects of active shock avoidance (ASA) learning on hippocampal progenitor proliferation and survival of newly formed cells were investigated. ASA training, although considered as hippocampus-independent, is known to induce several neurobiological alterations in the hippocampus. Adult Wistar rats were trained in a shuttle box using a 1-day or 4-day paradigm and brains were analyzed for the mitotic marker Ki-67. Effects on survival of newly generated cells were examined by immunocytochemistry for 5-bromo-2-deoxyuridine (BrdU), which was injected 1 week before the training. Neither proliferation nor survival was affected by the ASA learning task. Because elevated glucocorticoid levels have a negative impact on hippocampal neurogenesis, blood samples were taken throughout the 4-day training paradigm. Both trained animals and control rats that were only placed in the shuttle box without receiving foot shocks showed a similar rise in corticosterone, enabling us to exclusively investigate the effects of ASA learning on neurogenesis without differential interference of stress between groups. On the other hand, the finding that ASA induced elevations in plasma corticosterone, but did not influence proliferation or survival of newly formed cells, indicates that this type of stress does not affect neurogenesis. The present study shows that, in line with the existing data on other hippocampus-independent learning tasks, ASA training has no effect on hippocampal neurogenesis.

Analysis of Variance↗
PubMed1980

Passive avoidence learning in the young rat.

A step-through locomotor passive avoidance task is described requiring the suppression of a spontaneous escape reaction from a cool toward a warm compartment in order to avoid an electric shock delivered in the warm side. We observed no lerning of this task at 9 days of age, a very low but significant level of acquisition at 11 days, a slow but progressive improvement of avoidance from the 13th until the 17th day when the adult capacity was achieved, and a marked increase in the rate between 17-20 days.

Aging↗
PubMed1980

Subcellular localization of increased incorporation of [3H]fucose following passive avoidance learning in the chick.

The effect of training on a passive avoidance test on incorporation of [3H]fucose into subcellular fractions of the anterior forebrain roof of 1-day-old chicks was determined. Isotope was injected intraperitoneally, and birds tested and killed after 3 h. There was an increase in incorporation in trained compared with untrained control birds in the synaptic membrane (19% elevation, P less than 0.02) and the mitochondrial (14% elevation, P less than 0.05) fractions. Following intracranial injection, increased incorporation in trained birds was seen only in the synaptic membrane fraction (39% elevation, P less than 0.01); this increase in incorporation was not limited to any particular electrophoretically separated glycopeptides, but occurred in all 9 detected peaks.

Animals↗
PubMed1991

Intertrial responses of rats in two-way avoidance learning to visual and auditory stimuli.

Learning and performance of two-way avoidance were investigated in a total of 68 rats trained with either a visual (change in illumination to darkness or to light) or an auditory (white noise of 70 or 60 dB intensity) conditioned stimulus (CS). Experiment I showed that the darkness CS produce lower avoidance performance and a much higher rate of intertrial responses than either a auditory or a compound (visual plus auditory) CS. A monotonic within-session increase of avoidance performance and a similar, but less regular increase of intertrial responses were found at the beginning of training in each group. In later sessions such trends were observed only in rats trained with a visual CS. Experiments II and III showed also rapid transfer of avoidance response and a corresponding change of intertrial response rate with the change of CS modality. When the compound CS was used, the effects of the visual element were completely overcome by the auditory one. Rats trained with a visual CS in Experiment IV showed a positive correlation between avoidance performance and the number of intertrial responses, which was more pronounced in earlier than in later training sessions. We consider the rise of intertrial behaviour as an adaptive response to the increase of task difficulty. CSi of different modalities differ not only in relative saliency, but also in the discriminability between their onset and offset. The modality of the CS influences not only avoidance performance but also the course of learning.

Acoustic Stimulation↗
PubMed1984

Effects of caffeine on aggressive behavior and avoidance learning of rats with isolation syndrome.

Caffeine at a dose of 40 mg/kg i.p. administered 60 min before testing for aggressive mouse-killing behavior in Wistar rats with isolation syndrome inhibited mouse-killing response in 48 per cent of the aggressive rats. When injected 60 min before two-way active avoidance training caffeine improved learning in grouped rats, did not facilitate it in isolated non-aggressive rats and significantly improved avoidance behavior in isolated aggressive rats. The antiaggressive effect of caffeine is most probably due to its inhibitory action on phosphodiesterase and the resulting increase of brain cAMP, to the provoked increase of brain 5-HT and to its binding to brain benzodiazepine receptors. The positive effect of caffeine on avoidance learning of isolated aggressive rats is likely due to its indirect stimulant action on the brain dopaminergic system.

Aggression↗