Biomedical subjects

I Lukaszewska

Publications and source records attributed to I Lukaszewska.

At least 19 recordsLinked to original sources

PubMed1997

Naloxone impairs spatial performance in rats.

Naloxone-injected (1.0 mg/kg) and saline-injected control rats were subjected to a two-trial test of object localization memory. In trial I rats were allowed to explore for 5 min an enclosed T-maze with an object (plastic bottle) placed in one maze arm. Then, the object was removed and after a 20-min retention interval rats were faced with two empty arms of the same maze (trial II). Control rats showed good retention of the place occupied by the object, displaying a significant preference (74%, P < 0.032) for the arm which previously contained the object. Naloxone treated rats responded at chance levels (53%). An accurate performance in this task is normally based on information provided by spatial cues outside the maze (cognitive map), so that a random performance of Naloxone treated rats could supposedly be related to some disorders in the internal representation of the environment.

Animals↗

PubMed1997

The effect of naloxone on object exploration, object recognition and other types of spontaneous behavior.

Object exploration was examined in naloxone injected (1 mg/kg or 4 mg/kg) and saline control rats. Naloxone rats explored an object for a shorter time than did controls, thus indicating a lower investigatory motivation. This effect was dose dependent. Higher drug dose (4 mg/kg) decreased the number of contacts with an object. Both doses increased the mean duration of contacts with an object. The naloxone groups showed intact recognition of a familiar object paired with a new one in two sessions--4 h and 24 h after the injections. The higher drug dose depressed the locomotor activity and wall leaning. Grooming was not influenced by naloxone. The normal daily fluctuations in the level of grooming and locomotion were distorted following the injection of the higher dose of naloxone. The lower dose (1 mg/kg) did not affect the rats' performance in some tests. The results could be viewed as a naloxone-related depression of the behavior containing motor elements like locomotion, wall leaning and object approaching. The prolonged contact time with an object could be the result of a lowered flexibility of movement. However, the decrease of rewarding value of exploration could not be ruled out. Possibly, naloxone exerts several different interacting behavioral effects.

Animals↗

PubMed1995

The differences in learning abilities between spontaneously hypertensive (SHR) and Wistar normotensive rats are cue dependent.

We examined the performance of spontaneously hypertensive (SHR) and Wistar normotensive (NT) rats in acquisition, retention after a 2-month interval, and reversal learning in two tasks: simultaneous brightness discrimination (Experiment I) and conditional discrimination of directional locomotor responses (Experiment II). In both tasks food reinforcement was used. In Experiment I both SHR and NT groups comprised younger (3-month-old) and older (10-month-old) rats. In each experimental stage SHRs of both age groups mastered the task earlier and made fewer errors than the respective NT groups. Reversal learning took longer than acquisition of discrimination in both age groups of NT rats. Conversely, reversal learning was an easier task for SHR. In Experiment II only younger rats were used. The forced turn at the start in the modified T-maze was utilized as the cue to guide performance at the choice point of the maze. In acquisition and retention, rats were trained to select at the choice point the arm in the same direction as in the forced turn; in the reversal, opposite contingencies were applied. At all stages the choice accuracy of SHR was the same as that in NT rats. The contrasting findings of Experiment I and Experiment II indicate that SHR learned better than NT when exteroceptive visual stimuli were used, but performed at the same level as NT rats in the task where interoceptive kinesthetic cues were relevant. We suggest that SHR pay more attention to visual stimuli than NT rats.

Age Factors↗

PubMed1994

Object recognition is not impaired in old rats.

Twenty two months old and eight months old rats were used. They were submitted to object recognition test with 1 min interval between two successive presentations of the same object or two different objects. Initial exploration of the object was lower in aged than in young rats. However, both groups showed comparable habituation of exploratory responses in the presence of the familiar object. The changed object did not produce the decrease of exploration. These findings provide further evidence that memory involved in object recognition is not affected by aging.

Aging↗

PubMed1993

Scopolamine affects response-to-change test involving 20-min retention interval after locomotor exploration in rats.

The tendency to select the T-maze arm that has been changed in brightness between two successive trials (response-to-change) was investigated. Our previous findings indicated that scopolamine injections (1.0 mg/kg) impaired responding to change of brightness in a choice trial (trial II) following a 1-min retention interval, when in the first acquisition trial rats could only inspect the white-black T-maze arms through transparent partitions (the passive test). The drug was ineffective when rats were allowed locomotor exploration of the maze (the active test). The aim of the present experiment was to investigate the effect of the same dose of scopolamine on the active test involving a longer 20-min retention interval between the acquisition trial and the choice trial. The effect of cue salience also was examined by using grey-black arms. Rats injected with scopolamine (Scopo) 20 min before the acquisition trial performed in the white-black maze on the chance level, whereas saline-injected rats (Sal) showed significant preference for the changed arm. Decreasing the cue salience impaired response-to-change in Sal rats (50% of changed arm choices) but had no further effect on performance of Scopo rats, presumably because of a floor effect. The postacquisition injection had a somewhat stronger effect than the injections preceding acquisition, which most probably reflects the state dependency phenomenon. The deficient performance due to scopolamine treatment that appeared in the present study at a longer retention interval could be interpreted in terms of increased forgetting.

Animals↗

PubMed1993

Scopolamine impairs object exploration but not habituation in rats.

Memory of a novel object was examined in saline (Sal) and scopolamine (Scopo) treated rats (1.0 mg/kg). Scopo rats showed lower overall exploration time than Sal rats, resulting mainly from shorter durations per contact. In a second exposure to the same object, after 1 min or 20 min interval, both groups displayed marked decrease of exploration indicating between-session habituation. The shorter time spent by Scopo rats on investigation of an object during a single approach might be interpreted as a deficit in maintenance of attention. Nevertheless, Scopo rats were able to acquire sufficient information for the retention during 20 min interval, as indicated by habituation, which is an elementary index of memory.

Animals↗

PubMed1990

Memory restoration or memory block: differential effects of physostigmine depend on the age of the memory trace.

The authors investigated the effect of physostigmine (Ph) on short-term memory underlying the response-to-change test in rats. In the first test trial (acquisition) the rat could observe the white-black T-maze arms through transparent partitions which prevented the entrance to the arms. In the subsequent trial the rat was allowed a free choice between two identical maze arms, one of them being changed from white to black or vice versa. Physostigmine or saline (NaCl) was injected i.p. 1 min after the acquisition trial. When the retention interval between the two trials was short (10 min), NaCl rats showed a significant preponderance of the changed arm choices, whereas after a longer retention interval (20 min) they selected the changed arm in low percentage. This indicated a rapid decline of memory traces underlying the response to the change of brightness. Physostigmine in a dose of 0.1 mg/kg blocked responding to change after 10 min retention interval, when the memory was strong. However, when tested after a 20 min interval, Ph injected rats showed restoration of memory. After a 15 min interval, retention in both NaCl and Ph injected rats was on a similar, intermediate level. A higher dose of Ph (0.3 mg/kg) had no effect on responding to change after any retention interval examined in this experiment.

Amnesia↗

PubMed1989

The role of body turn-brightness associations in the effect of scopolamine on response-to-change in the rat.

We explored further the different effects of anticholinergics on response-to-change in the passive and active tests. We hypothesized that body turn-brightness associations are formed in the active but not in the passive test, where the turns were prevented by transparent partitions blocking maze arm entrance. This difference might account for the resistance of the active test performance to anticholinergic drugs. To examine this idea, the passive test conditions were modified so that body turns were possible. However, scopolamine (1.0 mg/kg) interfered with response-to-change performance to the same extent as observed previously in the typical passive test procedure. Thus, body turn-brightness associations are not the source of resistance of active test performance to cholinergic receptor blockade.

Animals↗

PubMed1988

Cue distinctiveness and response-to-change in scopolamine injected or hippocampal rats.

Our previous findings indicated that hippocampal lesions (H) or scopolamine' injections (Sc) affected stimulus information acquired by distant observation of the white-black T-maze arms (the passive test), but left the information intact when it was gained by T-maze exploration (the active test). Because this difference might reflect the attentional deficit in H or Sc rats, in the present experiment we attempted to investigate the effect of lowered distinctiveness of cues (dark grey vs black T-maze arms) on the performance of rats in the active test. A total of 75 rats were assigned to four groups: (i) damaged in the dorsal hippocampus (H); (ii) sham operated (C); (iii) scopolamine (Sc) injected (1.0 mg/kg i. p.) and (iv) saline injected (NaCL). Each group showed a significant preponderance of choices of the arm which was changed in brightness between the two consecutive trials, separated by 1 min break. The groups did not differ markedly among themselves in the percentage of changed arm choices (H group, 85 percent; C, 74 percent; Sc -72 percent; NaCL, 72 percent). This result indicates that H or Sc rats are able to perceive a slight difference of brightness and to retain it over a period of 1 min. Therefore, the different performance of H as well as Sc rats in the passive and active test, observed previously, cannot be accounted for by the attentional deficit hypothesis.

Animals↗

PubMed1988

Some evidence of enhanced alimentary motivation in spontaneously hypertensive rats (SHR).

The consumption of a wet mash of biscuits or pellets, outside the home cage, was determined in adult spontaneously hypertensive (SHR) and normotensive (NT) Wistar rats. Rats were deprived of food for 24 h or satiated. Regardless of the testing conditions, SHR showed a higher food interest than NT rats, which was reflected in a shorter latency to start eating, a longer time of eating to the first interval as well as to the 30 sec interval which terminated the trial, and a larger amount of food consumed during the test trial. The speed of eating was greater in SHR. In the competition for food SHR won almost all encounters with NT rats. The mean time of eating by SHR increased over the consecutive encounters up to 90%. These findings indicate that alimentary motivation of SHR was higher than that of NT rats. The results are discussed in terms of hyperreactivity of SHR.

Animals↗

PubMed1987

Increase in body weight of spontaneously hypertensive rats (SHR) under prolonged behavioral stimulation.

We noticed that during 44 weeks of exposure to a number of behavioral tests (such as assessments of emotionality, locomotion, short term memory and visual discrimination learning) the body weight of spontaneously hypertensive rats (SHR) increased above that of normotensive controls (NT). To determine whether this difference was related to "behavioral stimulation" resulting from different testing situations and accompanying handling, body weights were recorded in other SHR and NT groups not subjected to any experiment (unstimulated). Stimulated SHR were significantly heavier than rats from other subgroups (unstimulated SHR as well as stimulated and unstimulated NT rats) which did not differ from one another. The first significant difference appeared after 7 weeks of behavioral training (18th week of life). Several weeks later, and continuing for the duration of study, stimulated SHR were approximately 12% heavier than the other 3 groups. No effect of behavioral testing on blood pressure was seen in either strain.

Animals↗

PubMed1986

Effects of atropine on response-to-change.

The effect of atropine on rats response to the change of brightness was investigated in a T-maze, in two procedural test versions differing in the exposure of visual stimuli. In the passive test the rats could observe the white and black arms through clear partitions which blocked the entrance to the arms, while in the active test they were allowed to explore the maze arms. In the subsequent free choice trial, when both arms were of the same brightness (either white or black) atropine in a dose of 16 mg/kg, injected 10 min prior to the exposure of stimuli, affected the rats' performance in the passive test. The druged rats showed random selection of the arms, whereas 80 percent of saline controls chose the arm whose brightness had been changed. In the active test the same dose of atropine had no effect on the choice behavior. Both atropine and saline groups showed a closely similar preference for the changed arm. The effect of atropine on response-to-change was compared to that of scopolamine investigated by us in the previous study.

Adaptation, Psychological↗

PubMed1985

Scopolamine impairs the response-to-change following observation of the environment but not after its exploration by the rat.

The tendency to select the T-maze arm that has been changed in brightness between two successive trials (response-to-change) was investigated in rats injected with scopolamine (Sc) or saline (NaCl) 20 min before the test. In the "passive" version of the test, when in trial 1 rats could inspect the white-black arms through clear partitions blocking the entrance to the arms, a dose of when in trial 1 rats could inspect the white-black arms through clear partitions blocking the entrance to the arms, a dose of 1.0 mg/kg Sc decreased significantly the number of changed arm choices in trial 2, as compared to saline controls. A lower dose of Sc (0.5 mg/kg) was ineffective. In the "active" test version, when in trial 1 the rats were allowed to explore the white-black arms, doses of 1.0 and 2.0 mg/kg Sc did not affect the preference for the changed arm in trial 2. NaCl rats showed a significant preference for the changed arm choices in both tests. The scopolamine effects on response-to-change, i.e., impairment of performance in the passive but not in the active version, were essentially the same as those found by us previously in hippocampal rats.

Adaptation, Psychological↗

PubMed1984

Food-motivated behavior in rats with cortico-basomedial amygdala damage.

Twelve rats with amygdala damage (CBM) and 20 sham-operated controls were tested in several food-related situations. The CBM rats showed a longer latency to eat than controls in a novel environment due to more pronounced exploration. In the competition for food, CBM rats lost 85% of encounters with controls. Immediately after the contest, when allowed to eat singly, CBM rats displayed a higher persistence of alimentary responses to an emptied cup than did controls, presumably because they experienced more losses in the food competition. Both groups were equally able to overcome obstacles on the way to food, which suggests similar alimentary motivation. The only direct indication of a lowered responsiveness to hunger in CBM rats was 24-hr-fasting-induced hypophagia. The results of this study indicate the involvement of the cortico-basomedial amygdaloid region in the control of relations between alimentary and other motivations. The contribution of eventual changes of food motivation in the postoperative alteration of this balance is discussed.

Amygdala↗

PubMed1983

Response to stimulus change: amygdalar lesion elicits similar deficit as hippocampal damage.

We attempted to test whether the effect of amygdaloid lesion on the response-to-change would be similar to that observed previously after hippocampal damage. Twelve rats with lesions in the cortico-basomedial region of the amygdala (CBM) and 20 sham operated controls were used. The experiment was conducted in a T-maze under two different conditions of stimulus presentation in trial 1. In the passive test the rat was allowed to inspect the white-black maze arms, but was prevented from entering them by transparent partitions. In the active test the rat was permitted to explore the entire T-maze. In both tests, the brightness of one arm was changed in trial 2, so that the two arms were alike. Control rats showed a statistically significant pre-ponderance of choices of the changed arm in both tests. CBM rats responded on a chance level in the passive test, while in the active one they performed like controls. These results, replicating closely the previous findings on rats with hippocampal damage, indicate the involvement of both the amygdala and hippocampus in the passive version of the response-to-change test. The postoperative disturbance might be interpreted as an attentional deficit or a selective impairment of information processing in the passive version of the test.

Amygdala↗

PubMed1982

How long do rats remember the spatial arrangement of visual stimuli?

The responses to stimulus change consisting in the choice of maze arm where the brightness was changed between two consecutive trials were studied in an enclosed T maze with varying exposure times and retention intervals. The strength of memory involved in the response-to-change test depended on both variables. Memory acquired in 10 min exposure survived around 25 min, while after 1 min exposure memory decayed in less than 15 min. Under conditions of paucity of memory traces rats relied on their directional preferences.

Animals↗

PubMed1982

Response to stimulus change following observation or exploration by the rat: a confirmation of differential effects of hippocampal damages.

The experiment attempted to confirm the previous finding that hippocampal lesions in rats affected the information acquired by distant observation of the brightness difference of the T-maze arms, but left the information intact when it was gained by maze exploration. An alteration was introduced in the latter procedure allowing a complete elimination of olfactory stimuli, which might be utilized as nonmemorial cues. Despite this alteration the results were virtually the same as previously. Following maze exploration the hippocampally lesioned rats tended to enter the arm that had been subsequently changed in brightness, similarly to control rats. However, unlike the controls, they responded on the chance level after distant observation. This finding is not compatible with Oltons hypothesis postulating the involvement of the hippocampus in the working memory, or with the OKeefe-Nadel theory of processing spatial information by the hippocampus.

Animals↗

PubMed1981

Open-field behavior in rats with frontomedial cortical, neostriatal or hippocampal lesions.

The effects of lesions in four structures corresponding to the main components of dorsal prefrontal system of the monkey were studied in a total of 165 rats. In a homogeneous open-field apparatus, rats with frontomedial cortical (FM) or anteromedial neostriatal (NC) lesions showed more ambulations than their respective sham operated controls. Posteroventral (VH) and anterodorsal (DH) hippocampal damages did not affect ambulations. The introduction of a novel stimulus produced transient suppression of open-field activity in all lesioned and control groups. Exploratory responses to the stimulus, assessed by the number of direct contacts and the time spent near the stimulus, were fewer in rats with VH or DH lesions than in rats with FM or NC lesions, that in turn did not differ from controls in this respect. Fear, indicated by defecations during the entire open-field test and by prolonged activity suppression in response to the presence of the novel stimulus, was observed in FM or VH lesioned rats, but not in those subjects with NC or DH lesions. Functional interrelations among these structures are discussed relative to their participation in a common functional system.

Animals↗