Biomedical subjects

M Dahhaoui

Publications and source records attributed to M Dahhaoui.

7 recordsLinked to original sources

PubMed1997

Effect of cerebellar granule cell depletion on spatial learning and memory and in an avoidance conditioning task: studies in postnatally X-irradiated rats.

Rats of the DA/HAN strain (pigmented rats) were submitted to two experimental tasks consisting in spatial learning (water escape experiment) and in passive avoidance conditioning. These rats were either totally or partially deprived of their granule cells using two different schedules of postnatal X-irradiation of the cerebellum. When they were 3 months old, the animals were submitted to an initial learning session, followed by a retrieval test seven days later. The scores of the rats which were partially deprived of granule cells appeared similar to those of controls, except for a mild deficiency of spatial learning. The learning and retrieval scores of the rats totally deprived of granule cells were similar to those of controls at the passive avoidance conditioning task, but these animals were unable to accurately learn a spatial task and showed memory impairments relative to controls. These results are discussed in terms of cognitive defects.

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PubMed1994

Effects of inhibition of the GABAergic systems by picrotoxin on retention of a nociceptive experience in the rat, with special reference to the influence of cerebellar cortex output.

Adult cerebellectomized and noncerebellectomized DA/HAN strain (pigmented) female rats were submitted to a one-trial passive avoidance conditioning procedure consisting in associating darkness with a nociceptive stimulus. Seven days later, they were tested again to assess the retention stage. The results demonstrate that in noncerebellectomized rats, picrotoxin, whatever the dose, administered prior to the retention test, does not significantly impair retrieval. On the contrary, when administered just prior to the initial conditioning, impairments of the initial single nociceptive experience were evident (the greater the picrotoxin dose, the greater the impairments). In animals that were cerebellectomized 1 week before the experiment, picrotoxin administered at a low dose before the initial experience elicited memory impairments that were similar to those induced in noncerebellectomized rats but that were greater than those elicited in cerebellectomized, nontreated animals. However, in cerebellectomized rats, picrotoxin administered at a low dose elicited memory impairments that were weaker than in noncerebellectomized animals injected with a high dose of the drug. Considering that a low dose of picrotoxin administered to cerebellectomized animals had effects that were similar to those of a high dose injected to noncerebellectomized rats, and given that it has previously been demonstrated that a cerebellectomy performed after a single nociceptive experience impairs its memory, it is tempting to suggest that the two different doses of the drug administered to cerebellectomized and noncerebellectomized rats have similar effects on memory. If such an interpretation is valid, the information would have to leave the cerebellar cortex to be stored for long.

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PubMed1992

Effects of lesion of the inferior olivary complex by 3-acetylpyridine on learning and memory in the rat.

DA/HAN-strained male rats (pigmented rats) were submitted to two experimental tasks consisting of spatial learning (water-escape) and a passive avoidance conditioning. Both these tasks were performed by different animals. In order to destroy the inferior olivary complex, the animals were injected with 3-acetylpyridine either 9 days prior to the initial learning session or 24 h after completion of the learning task. They were retested (retrieval test) 10 days after the initial learning was achieved. Learning and retention were compared to those noted in control rats. Administration of 3-acetylpyridine before the initial learning did not prevent the spatial learning but the scores were greatly altered and the number of trials needed to reach the fixed learning criterion was much greater than in controls. However, 10 days later the animals had memorized their initial experience. Injection of 3-acetylpyridine after the initial learning session impaired memory: the animals had completely forgotten their initial learning. It can therefore be concluded that lesion of the afferent climbing fibres to the cerebellar cortex alters learning and retention of a spatial task. Such a lesion does not interfere with learning and retention of a passive avoidance conditioning, since in this condition the experimental animals injected with 3-acetylpyridine either before or after the initial learning behave similarly to controls. The effects of the inferior olivary complex lesion are obviously different according to the task to be learnt, suggesting that these two tasks do not require the integrity of the same nervous structures.

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PubMed1992

Role of the cerebellum in habituation exploration behavior in the rat.

Adult control and cerebellectomized DA/HAN-strained male rats were submitted to habituation of exploration behavior in a test environment consisting of a novel cage in which four objects were displayed. Seven days after the initial session of habituation, retention of the habituation was tested. Within-session habituation was observed in cerebellectomized and control rats. However, retention of habituation was impaired in rats that were cerebellectomized after the initial session but not in those cerebellectomized before the session. These results are consistent with the hypothesis that the cerebellum has a role in memory of habituation to environmental stimuli.

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PubMed1992

Role of the cerebellum in spatial orientation in the rat.

Adult DA/HAN strain rats were submitted to a spatial orientation task consisting of finding a reward in an open field. They were first submitted to an initial learning session and 10 days later to a retrieval test. The animals were divided into four groups of five rats each: animals that were cerebellectomized before the initial learning session or after the initial learning session, sham-operated rats, and control (intact) animals. Different parameters that characterize the spatiotemporal organization of the rat's exploratory behavior were quantified. From the results, it can be concluded that the cerebellum is not absolutely necessary in the processes that sustain spatial learning but that it is involved in the mechanisms sustaining focused spatial memory and in the cognitive processes of the motor program elaboration and not only in the regulation of the movement being done.

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PubMed1991

Cerebellum and memory: an experimental study in the rat using a passive avoidance conditioning test.

Adult DA/HAN strain rats were submitted to a one-trial passive avoidance conditioning procedure consisting in associating darkness with a nociceptive stimulus. Seven or fourteen days after the one-trial initial experience, they were tested again in order to know whether they had forgotten it or not. The animals were divided into two experimental groups, the rats being either conditioned (COC group) or not (NOC group) before cerebellectomy, and two control groups, the animals being either intact (C group) or sham-operated (SO group). Each group was divided into two subgroups, one being given the retrieval test 7 days and the other 14 days after the initial conditioning. The results show that retention in C, SO and NOC rats was similar whether the animals were tested 7 days or 14 days after the initial one-trial conditioning. Seven days after their initial experience and the cerebellectomy, the retention in COC rats was null while when they were tested 14 days after cerebellar removal these animals had much better scores, significantly higher than 7 days after the lesion. It is concluded that the cerebellum is involved in the consolidation processes of the memory trace but is not the site of memory storage.

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PubMed1990

Role of the cerebellum in an avoidance conditioning task in the rat.

Adult DA/HAN strain male rats were submitted to an avoidance conditioning procedure. They were divided into two experimental groups, the animals being either conditioned (COC group) or not (NOC group) before cerebellectomy, and two control groups, the animals being either intact (C group) or sham-operated (SO group). Although the NOC rats could be conditioned successfully and the cerebellum is not absolutely necessary for the avoidance conditioning achievement, their scores were significantly lower than the preoperative scores of COC rats. Moreover, the scores of NOC rats (postoperative scores) were significantly lower than the postoperative scores of COC animals, suggesting that the preoperative conditioning makes the postoperative conditioning easier. At last, comparing postoperative scores of COC rats with those obtained by C and SO rats when given the retrieval test and comparing preoperative and postoperative scores in COC animals show that retention of the initial (preoperative) conditioning is partly abolished by the cerebellectomy. Histological controls demonstrated that the entire cerebellum except for the flocculus and the nodulus was removed. These results strongly suggest that the cerebellum is involved in the memory processes that sustain the avoidance conditioning.

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