Biomedical subjects

I Morgado-Bernal

Publications and source records attributed to I Morgado-Bernal.

26 records · Page 2Linked to original sources

PubMed1991

Improvement of shuttle-box avoidance with post-training intracranial self-stimulation, in rats: a parametric study.

Rats were trained in a two-way active avoidance task followed immediately by a lateral hypothalamic intracranial self-stimulation (ICSS) treatment, during 5 consecutive days. The effects of the number of ICSS trains allowed (0, 500, 2500 or 4500) were studied upon acquisition and long-term retention (LTR, 10 and 30 days). The number of ICSS trains administered and the number of avoidances at the last acquisition session (5th) showed a positive lineal relation, that is, the more number of ICSS trains, the more number of avoidances. The level of learning achieved during the 5th session was maintained after the LTR periods in all experimental groups. It is concluded that the number of ICSS trains could be a critical parameter in the facilitatory effect of lateral hypothalamic ICSS upon learning, and it is suggested that the facilitatory effect of post-training lateral hypothalamic ICSS might be due to the activation of general activatory neural systems.

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PubMed1991

Facilitation of shuttle-box avoidance by the platform method: temporal effects.

Two experiments were carried out in order to 1) replicate a previous finding according to which the treatment on large platforms (commonly used as control for the stress induced by smaller paradoxical sleep deprivation platforms) can facilitate the acquisition and long-term retention (LTR) of a distributed shuttle-box avoidance in rats, and 2) further examine the temporal conditions in which that facilitation can be observed. The results showed that an immediate posttraining treatment lasting 6 hours induced a significant improvement of acquisition both when applied in the light (8 a.m.) and in the dark cycle (8 p.m.), while the LTR (10 and 31 days) seemed to be better preserved when the treatment was applied during the dark cycle. A shorter treatment (3 h) had no effect upon shuttle-box avoidance, regardless of whether it was applied in the dark or in the light cycle and whether it was immediate or delayed for 3 h. In summary, under certain temporal conditions, a posttraining immediate treatment on large platforms can facilitate the acquisition and/or the LTR of shuttle-box avoidance. Stress hormones and/or the enhancement of CNS arousal are suggested to be some of the mechanisms operating in this facilitatory effect.

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PubMed1989

Behavioral evaluation of the stress induced by the platform method for short-term paradoxical sleep deprivation in rats.

To evaluate whether the results of short-term PSD (Paradoxical Sleep Deprivation) using the platform method can be influenced by stress, changes in body weight and in behavioral indices (food and water intake and ambulation and defecation in an open field) were measured in rats after each of four 5-hour sessions of confinement to small or large platforms. The animals of the two platform groups when compared to animals kept in home cages showed a similar decrease in body weight which was significant only after the first day of treatment, while no changes in the other measures were observed. It is concluded that 1) the effects of stress induced by short-term confinement to platforms do not seem to be a remarkable confounding factor in short-term PSD studies and 2) large platforms can be used both as an adequate stress control for small platforms and as a means of adapting the animals to the method.

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PubMed1989

Correlations between paradoxical sleep and shuttle-box conditioning in rats.

Eighteen male Wistar rats were given one daily two-way active avoidance conditioning session followed immediately by 5 hr of sleep recording, for 5 consecutive days. The group of rats that achieved 80% or greater avoidance in some of the 5 training sessions showed significant linear increases of paradoxical sleep (PS), compared with baseline levels, throughout the successive conditioning sessions. Furthermore, (a) the group of rats showing PS increases (more than 1 SD above baseline) after some of the training sessions achieved a significantly higher final number of avoidances than the remaining animals: (b) a high and positive correlation was observed between avoidance increases in the 3rd conditioning session and previous PS; and (c) maximum increases in correct performance often occurred following high PS increases. It is concluded that PS increases facilitate the consolidation of learning.

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PubMed1988

Improvement of shuttle-box avoidance following post-training treatment in paradoxical sleep deprivation platforms in rats.

The effects of post-training paradoxical sleep deprivation (PSD), via the platform method, on acquisition and long-term retention (LTR) of shuttle-box avoidance were studied in Wistar rats. Animals had a daily training session for 5 days (acquisition), following which each rat was placed for 5 hr either on a small platform (7 cm) surrounded by water (PSD group) or on a large platform (16 cm) surrounded by water (Yoked control group), or was given no treatment (Dry control group). Another identical training session (LTR test) was also given to every subject 14 days after the last acquisition session. The treatment on the large platform (Yoked animals) improved learning in successive training sessions. A similar but not statistically significant improvement was also observed in the PSD group. In the LTR test, the PSD animals tended to decrease performance as compared with the conditioning level achieved in the previous acquisition session. Locomotor and emotional changes produced by PSD and PSD procedures are ruled out as the cause for these findings. We suggest that arousal produced by both PSD and PSD procedures could have improved the acquisition of the conditioning, whereas PSD per se could have been detrimental for LTR of the learned response.

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PubMed1988

Improvement of shuttle-box learning with pre- and post-trial intracranial self-stimulation in rats.

The effects of intracranial self-stimulation (ICSS) in the lateral hypothalamus upon the acquisition and long-term retention (LTR) of shuttle box avoidance conditioning were studied in Wistar rats. Two groups of subjects learned the avoidance task in 5 daily training sessions and were allowed to self-stimulate either before (Pre-ICSS group), or after (Post-ICSS group) each training session. A control group received training but no ICSS. Ten days following the last training session, LTR of the task was determined in one avoidance session without ICSS. A fourth group was added post-hoc which was allowed to self-stimulate before the training sessions as well as before the LTR test. Both the Post-ICSS and Pre-ICSS groups improved in acquisition of the learned response over the successive training sessions, as compared with Controls. In the LTR test, the animals of the Post-ICSS group maintained the response level achieved in the last acquisition session. In contrast, the subjects of the Pre-ICSS group showed a significant decrease of the same response, unless they were given ICSS treatment prior to the LTR test. This may indicate a 'state-dependent learning' effect being responsible for the decrease in the LTR observed in Pre-ICSS group. Because both pre- and post-training ICSS treatments improved the acquisition and the LTR of the learned response, it is suggested that the contingency of the treatment with training (that is, ICSS treatment immediately after the training sessions) is not a necessary condition to facilitate the acquisition and the consolidation of two-way active avoidance learning.

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PubMed1987

Effects of acute nicotine and ethanol on medial prefrontal cortex self-stimulation in rats.

The acute effects of nicotine and ethanol were studied in low and high rates of intracranial self-stimulation (ICSS) of the medial prefrontal cortex (MPFC) in the rat. Nicotine tended to increase low ICSS rates but did not change or even reduced high ICSS rates. Independent of ICSS rate, ethanol tended to decrease ICSS, but only at high doses (1.0 g/kg). It is suggested that the effects of nicotine and ethanol on ICSS may be mediated by their effects on dopamine.

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PubMed1984

Intracranial self-stimulation after paradoxical sleep deprivation induced by the platform method in rats.

Lateral hypothalamic intracranial self-stimulation was studied before and after paradoxical sleep deprivation (PSD) induced by the platform method. Rats were assigned to two counterbalanced groups where the sequence order of experimental (small platform) and control (large platform) treatments was permuted. In contrast with previous findings significant changes in the response rates for intracranial self-stimulation were not observed after PSD. Ineffectiveness and nonspecific effects of the treatment are ruled out as the cause for our findings. An hypothesis is suggested that the effect of PSD upon intracranial self-stimulation could be dependent of the brain electrode location.

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