Biomedical subjects

J Delacour

Publications and source records attributed to J Delacour.

At least 37 records · Page 2Linked to original sources

PubMed1989

Prenatal ontogenesis of brain phenolamines and catecholamines in relation to their metabolizing enzymes in Roman avoider strains of rats.

Phenolamines, particularly octopamines, are of special importance in avoidance behavior. In the Roman low avoidance (RLA) strain, p-octopamine can induce locomotor behavioral activity that is normally observed in the Roman high avoidance (RHA) strain. For these reasons, the levels of prenatal octopamines (para and meta isomers) have been studied in relation to noradrenaline and dopamine levels. In the hypothalamus and brainstem of RHA, a maximum level of the para isomer is observed at 15 days of embryonic development but, unlike in controls and RLA animals, this level remains almost constant until 20 days. For the meta-isomer and catecholamines, there is a 1-2 day delay in detection between controls and RLA or RHA. The study of related enzyme activities reveals that tyrosine hydroxylase displays a 2-day delay in RHA when compared to the control value at 19 days of fetal life. These results are discussed in terms of the role of p-octopamine in avoidance conditioning and of the possible delayed expression of the tyrosine hydroxylase gene in Roman strains of rats.

2-Hydroxyphenethylamine↗

PubMed1988

A new one-trial test for neurobiological studies of memory in rats. 1: Behavioral data.

In this paper we describe a new memory test in rats, based on the differential exploration of familiar and new objects. In a first trial (T1), rats are exposed to one or to two identical objects (samples) and in a second trial, to two dissimilar objects, a familiar (the sample) and a new one. For short intertrial intervals (approximately 1 min), most rats discriminate between the two objects in T2: they spend more time in exploring the new object than the familiar one. This test has several interesting characteristics: (1) it is similar to visual recognition tests widely used in subhuman primates, this allows interspecies comparisons; (2) it is entirely based on the spontaneous behavior of rats and can be considered as a 'pure' working-memory test completely free of reference memory component; (3) it does not involve primary reinforcement such as food or electric shocks, this makes it comparable to memory tests currently used in man.

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PubMed1988

Effects of piracetam on learned helplessness in rats.

In rats, the effects of Piracetam (P), the prototype of nootropic drugs, were studied on a very widely used model of behavioral disturbance: the learned helplessness (LH) phenomenon. In this model, exposure to uncontrollable and unsignalled shocks impairs subsequent escape-avoidance learning. In a first experiment, this deficit was abolished by 200 mg/kg of P, and to a lesser extent, by a 100 mg/kg dose, administered before the training session. In non-stressed animals, no dose of P was able to have a facilitatory effect on escape-avoidance. In a second experiment, the administration of P, not before the training session as in Experiment I, but before the stress, had no effect on the LH phenomenon regardless of the dose.

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PubMed1988

d-Amphetamine enhances memory performance in rats with damage to the fimbria.

Rats were preoperatively trained on a 5-unit linear maze and were then subjected to fimbria lesions. The animals were then retested on the same task with one group of rats with fimbria lesions and a control group being injected daily with 0.5 mg/kg d-amphetamine sulfate prior to testing. Lesions significantly impaired postoperative performance of the task, while amphetamine facilitated performance in fimbria lesioned rats. Due to an optimal learning of the task, performance of control animals was not significantly facilitated. These results raise several important issues including the mechanisms of functional recovery after brain lesions and the role of the hippocampal formation in learning and memory.

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PubMed1987

Effect of combined or separate administration of piracetam and choline on learning and memory in the rat.

Different groups of rats received combined or separate administration of different doses of piracetam (P1:100, P2:200, and P4:400 mg/kg) and choline (C1:100 and C2:200 mg/kg). Compared to control treatment, C1 significantly improved performance in a delayed alternation (DA) task, while P1, P2, P4 or P1C1 had no effect. Moreover, rats receiving P2C1 and P4C1 were significantly inferior in acquiring DA to rats receiving the vehicle or separate administration of P1, P2 or C1. The different treatments with combined or separate administration of P and C had no effect on spontaneous locomotor activity and two-way avoidance conditioning. In a recognition-task only groups C1 and P4 were able to discriminate between familiar and new objects. The combined or separate administration of P1 and C1 on NA, DA, DOPAC, 5-HT, 5-HIAA levels, CAT activity and choline uptake were measured in frontal cortex and hippocampus: the only significant effect was a 5-HT increase in the hippocampus of rats treated with C1.

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PubMed1987

Effects of selective lesions of fimbria-fornix on learning set in the rat.

The effects of selective partial lesions of the Fimbria-Fornix (FiFx) on reversal and place learning sets were investigated in rats by using a T-maze and a semi-circular multiple discrimination apparatus. Lesions restricted to the Fimbria (Fi) produced a significant deficit in reversal and place learning set, whereas lesions to the Fornix (Fx) only disturbed the learning set based on a reversal procedure. Combined Fi + Fx lesions resulted in impairment in the retention of spatial discrimination tested in the two mazes. Ventral Hippocampal Commissure (vhc) had no significant effect on reversal learning set. These results confirm previous data that the hippocampal formation is involved in learning transfer, and suggest that the Fi and the Fx may play a role in learning set. Our data also confirm previous demonstrations of the ability of rats to rapidly acquire place learning set.

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PubMed1987

"Learned" changes in the responses of the rat barrel field neurons.

The effect of pairing two vibrissa stimulations on unit responses of the barrel field of the somatosensory cortex were studied in partially restrained but awake and undrugged rats. Before pairing, one of the stimulations (S2) evoked a stable, short-latency and excitatory response from the recorded unit. Depending on the neuron, the other stimulation (S1), preceding S2 by 500 ms, did or did not have an effect before pairing. In a number of cases, the S1-S2 association produced significant changes in the unit responses: (1) the appearance of an excitatory response to S1 when that stimulus was ineffective before pairing; (2) the modification of pre-existing responses to S1 and/or S2. In all instances these modifications consisted in the decrease or disappearance of the "afferent inhibition" and/or the appearance of long-latency excitatory components. These effects appeared after some 30-100 trials and persisted in some cases up to 20 min after interruption of pairing. Our observations provide the first physiological data on the plasticity of the vibrissa projections in the chronic adult rodent. Though the underlying plastic neural elements and mechanisms remain to be specified, these phenomena suggest that "learned" changes in unit activity may occur in sensory systems and not only in "non-specific" ones.

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PubMed1987

Conditioning to time: evidence for a role of hippocampus from unit recording.

Unit activity of the dorsal hippocampus was recorded in partially restrained but awake and undrugged rats during a "conditioning to time". In this type of conditioning, only one stimulus, the equivalent of the unconditioned stimulus of the usual procedures, is used. It is delivered at a constant interval which, in principle, is the conditioned stimulus. In our experiments, the unconditioned stimulus was a mechanical stimulation of a vibrissa; two successive unconditioned stimuli were separated by a 24-s interval. In 11/18 rats, anticipatory movements of a "trained" vibrissa developed at the end of the interstimulus interval. In a number of cases, in parallel to this conditioned behavior, there was a significant change in unit activity, either an increase or a decrease, during the last third of the interstimulus interval. Controls showed that these changes in unit activity did not merely reflect modifications of arousal state or of vibrissa and body movements. From autocorrelograms, it appeared that anticipatory increases in unit activity were associated with the development of a bursting mode of discharge. These data constitute one of the rare examples of a neurophysiological correlate of a "conditioning to time" at the unit level and the first recorded from the dorsal hippocampus of rats.

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PubMed1986

High sensitivity of brain octopamine levels to stress.

Rats were submitted to unsignalled and uncontrolled electrical shocks. When re-exposed to the same situation but not shocked, 24 h later, their locomotor activity was significantly reduced compared to that of controls. This conditioned suppression was associated with a significant decrease in p-octopamine (OA) in brain stem and hypothalamus. Shocks delivered just before brain fixation produced an even larger decrease in cerebral OA. Heart levels of OA were not affected. Cerebral and peripheral levels of dopamine and noradrenaline were not significantly or reliably affected. These results, as those of previous experiments, suggest that octopamine is involved in emotional, neurovegetative responses to stress.

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PubMed1986

Psychophysiological profiles of the Roman strains of rats.

Male rats of the Roman High and Roman Low Avoidance strains were submitted to four principal behavioral tests: food-motivated acquisition of bar-pressing in Skinner box, delayed reinforced alternation, locomotor activity in a "multibox apparatus," conditioned suppression, and two biological measures: blood pressure and brain octopamine level. Performances of RLA and RHA rats were significantly different in each behavioral test. Blood pressure was higher in RHA, but the difference only approached the 0.05 threshold. As previously reported, brain octopamine levels of RHA rats were significantly higher than those of RLA. A multivariate treatment (analysis of correspondences) was applied to the data of 10 behavioral tests. The main factor extracted by this treatment clearly separated the two strains. Among the variables which best differentiate RHA and RLA rats, several do not involve stress (working memory, acquisition of bar-pressing, and locomotor activity).

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PubMed1986

Excimer laser surgery of the cornea: qualitative and quantitative aspects of photoablation according to the energy density.

Using an excimer laser working in the far ultraviolet and cutting fresh corneas of human cadaver eyes, we were able to demonstrate that there is an ideal fluence (joule/cm2/pulse) that allows a maximum tissue ablation depth per shot. Above the threshold of 1 J/cm2/pulse the depth of tissue ablated does not increase and both thermal and mechanical damage appears at the cut edges.

Cornea↗

PubMed1985

Differential acquisition of a "working memory" task by the Roman strains of rats.

Twenty-eight male rats of the Roman strains-fourteen RHA (Roman High Avoidance) and fourteen RLA (Roman Low Avoidance)-were submitted to a positively reinforced task, the delayed reinforced alternation test (DRA), in a T-maze. Performances of RLA rats were significantly better than those of RHA; RLA rats also had higher VTE (vicarious trial and error) and spontaneous alternation (SA) scores. These data confirm the fact that RLA may acquire positively reinforced learning as rapidly, or even more rapidly, than RHA rats, and that the differences in active avoidance behavior between these strains depend more on differential freezing behavior than on learning and memory capacities. Since the delayed reinforced alternation is considered as a working memory test, our results suggest that the Roman strains could be used as a genetic model for the neurobiological study of this form of memory.

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PubMed1984

Decrease in both choline acetyltransferase activity and EEG patterns in the hippocampal formation of the rat following septal macroelectrode implantation.

A decrease in both choline acetyltransferase (CAT) activity and theta (theta) rhythm were observed in the hippocampal formation of rats implanted with a macroelectrode in the dorsomedial part of the septum. The decrease in CAT activity and in theta occurred simultaneously and in parallel, and there was no instance where the two parameters were uncoupled. These observations suggest that a common neurophysiological mechanism is involved in both CAT activity control and theta rhythm production in the hippocampal formation. From a methodological point of view, these observations should be borne in mind in septohippocampal investigations using septal electrode implantation procedures.

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PubMed1984

Prenatal ontogenesis of p-, m-octopamine and phenylethanolamine in relation to catecholamines and their metabolizing enzymes in the developing rat brain and heart.

Non-catecholamines such as phenylethanolamine and p-octopamine are present in many invertebrate nervous systems, sometimes in large amounts. These amines are normally present in the rat brain at much lower levels, p- and m-octopamine are present at trace levels in the mammalian brain. The prenatal development of these amines was studied in comparison with those of noradrenaline and dopamine. The activities of tyrosine hydroxylase, dopa decarboxylase, dopamine beta-hydroxylase and monoamine oxidase were determined in parallel. Phenylethanolamine and p-octopamine are more abundant in the brain between 13 and 17 fetal days than dopamine and noradrenaline but decrease after 17 days whereas the levels of m-octopamine and the two catecholamines increase afterwards. Dopa decarboxylase, dopamine beta-hydroxylase and tyrosine hydroxylase are detected early in fetal life (13, 15 and 14.5 days respectively) but monoamine oxidase activity was not found before 18 days.

2-Hydroxyphenethylamine↗

PubMed1984

Two neuronal systems are involved in a classical conditioning in the rat.

Unit activity of the hippocampus, the centrum-medianum-parafascicularis and medialis dorsalis nuclei of the thalamus, was recorded in chronic rats during a classical conditioning; neocortical electroencephalographic and somatic responses were also recorded. Conditioned unit responses of the different groups of neurons were compared according to the precocity of their appearance, their stability, their latency and the differentiation between the positive (reinforced) and the negative (non-reinforced) conditioned stimuli. Conditioned unit responses of type I hippocampal neurons (probably pyramids) and of neurons located in the centrum-medianum-parafascicularis nucleus did not differentiate between the positive and negative conditioned stimuli; they progressed rapidly, then declined and disappeared. They were contemporary with an initial conditioning stage which was characterized by undifferentiated arousal responses (desynchrony of electroencephalographic activity) to both conditioned stimuli. Conditioned unit responses of type II hippocampal neurons (probably granule cells or interneurons of the fascia dentata) and of neurons located in the medialis dorsalis nucleus progressed slowly and differentiated between the conditioned stimuli during a late conditioning stage which was characterized by the regression of arousal responses and the differentiation of somatic responses. These data strongly suggest that two neuronal systems, each having a different role, are involved in classical conditioning in the rat.

Animals↗

PubMed1983

Brain octopamine and strain differences in avoidance behavior.

According to recent research, a significant relationship seems to exist between brain contents of p-octopamine and two-way avoidance responding in rats. Levels of this amine in hypothalamus and brainstem are higher in rats from the Roman High Avoidance (RHA) strain than in rats from the Roman Low Avoidance (RLA) strain. Intracerebroventricular administration of p-octopamine facilitates avoidance responding. The present paper reports the behavioral and neurochemical effects of p-octopamine administration on rats from the Roman strains. This treatment has no significant effect on cerebral levels of catecholamines, but it temporarily suppresses the strain differences in p-octopamine levels. In parallel, it also suppresses the strain differences in two-way avoidance conditioning, its facilitatory effect being much greater in RLA than in RHA rats. Avoidance behavior appears to be a useful model for the study of octopamine functions in the mammalian brain.

Animals↗

PubMed1983

Octopamine and locomotor activity of rats.

Intracerebroventricular administration of P-octopamine (OA) had opposite effects on locomotor activity depending on whether or not the rats were subjected to uncontrollable electric shocks. In unshocked rats, OA produced a large decrease in locomotor activity, but when the rats were subjected to unsignalled and uncontrollable electric shocks, a significant increase in locomotor activity resulted. The latter effect was observed either when the shocks were applied during the measurement of locomotor activity or when they were applied the day before (conditioned suppression paradigm). These results support the hypothesis of a neuromodulation of central noradrenergic transmission by octopamine.

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PubMed1983

Two-way avoidance behavior of the roman rat strains following brain lesions.

Rats of the Roman strains, Roman High Avoidance (RHA), Roman Low Avoidance (RLA) and Roman Control Avoidance (RCA) were submitted to 5 conditioning sessions in a two-way shuttle box; the sessions were separated by a 24 hr-interval. Two indices were computed: a within-session progression index W and an inter-session progression index I. Index W was comparable in all three strains; index I was strongly negative in RLA and equal to zero or slightly positive in RHA rats. Lesion of the hippocampal commissure (HC) significantly facilitated CAR acquisition in RLA by making index I less negative: performances of RCA and RHA rats were unaffected. Lesions of the centro medianum parafascicularis nuclei of the thalamus (CM) significantly impaired acquisition of CAR in RCA and RHA by making index I more negative; performances of RLA rats were unaffected. Neither lesion altered index W. These results support the "freezing hypothesis" in the explanation of the Roman strain differences. They are in agreement with recent data on the emotional characteristics of the Roman strains and on the role of octopamine in avoidance behavior.

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