Biomedical subjects

E Chleide

Publications and source records attributed to E Chleide.

9 recordsLinked to original sources

PubMed1991

Stimulant effect of the beta-carboline FG 7142 in the open-field test.

The anxiogenic activity of N-methyl-beta-carboline-3-carboxamide (FG 7142) is sometimes difficult to observe in rats. As the open field has recently been applied successfully to test the anxiogenic potential of n-butyl-beta-carboline-3-carboxylate (beta-CCB) in mice, a comparable experiment was performed with FG 7142 (1, 5, 10, 30 mg/kg i.p.) in rats. In contrast to the inhibitory effects measured with beta-CCB, FG 7142 significantly increased the ambulation and rearing scores and induced aggressivity in some animals. A differential sensitivity of mice and rats to beta-carbolines, predominant analeptic properties of FG 7142, and differences in the types of anxiety induced are proposed to account for this discrepancy.

Animals↗

PubMed1991

Effect of chronic hypoxic treatment on the retention of fixed-interval responding.

The present experiments aimed to study the effects of hypoxic treatment (10 min on 3.5% oxygen) on the stabilized performance of rats in a fixed-interval schedule (FI 60 s). The hypoxic treatment was given once a day, for 3 days, immediately after the FI session. The results showed that the operant performance was disturbed from the very first posthypoxia FI session. There was a sharp drop in response rate, and changes in the temporal distribution of responses occurred. The data obtained greatly limit the importance of nonspecific factors in explaining these changes in performance. The results are discussed with reference to the retrieval hypothesis. In particular, it is suggested that the decreases of performance may be due to an effect of hypoxia on the retrieval mechanisms associated with long-term memory.

Animals↗

PubMed1991

Effects of specific dopaminergic agonists and antagonists in the open-field test.

It has been found that dopaminergic transmission could be involved in some aspects of anxiety. The present study aims to explore this hypothesis further, using specific DA1 (SKF 38393) and DA2 (bromocriptine) agonists or DA1 (SCH 23390), and DA2 (zetidoline) antagonists in the open-field test. The results confirm previous studies indicating that DA1 and DA2 agonists predominantly increase locomotor activity, while DA1 and DA2 antagonists predominantly decrease it. However, at low doses, the four drugs increase the peripheral ambulation score significantly and, with the exception of zetidoline, also increase the central ambulation score. The observations made with zetidoline confirm the hypothesis that a specific presynaptic DA2 antagonism could be determinant for the disinhibitory effects of low doses of neuroleptics. A collateral action on 5HT transmission is also suggested to explain an hypothetic anxiolytic action of DA agonists and SCH 23390 at lower doses.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed1991

Enhanced resistance effect of piracetam upon hypoxia-induced impaired retention of fixed-interval responding in rats.

Rats were trained on a fixed-interval schedule of 60 s (FI 60). After stabilization of performance, rats were chronically submitted to hypoxic treatment (3.5% O2, 10 min) once a day, immediately after the daily FI 60 session. Hypoxia disturbed the retention of FI responding. It was mainly characterized by a decrease in response rate and in pause duration, and by changes in the temporal distribution of responses. Animals receiving piracetam (100 mg/kg, IP) 30 min before each FI session followed by hypoxia were significantly less affected than saline-treated animals. Results are discussed with reference to the effects of hypoxia and piracetam on nonspecific factors and on memory function. It is suggested that the effects of piracetam are due to alleviation of hypoxia-induced memory retrieval deficit rather than to a protection against hypoxic brain cell injury.

Animals↗

PubMed1990

Comparative study of the behavioral, neurophysiological, and motor effects of psychotropic drugs in the dog.

The purpose of this study was to present a comparative and detailed picture of behavioral, physiological, and motor effects of some barbiturates, benzodiazepines, and neuroleptics, using an operant procedure of differential reinforcement of response duration (DRRD) in the dog. An increase in response rate with low doses of barbiturates and benzodiazepines is interpreted in terms of behavioral disinhibition, anxiolytic effect, and enhancement of motivation. The depressive effects noted with higher doses of benzodiazepines and barbiturates, as well as with all doses of neuroleptics, can be explained in different ways. For benzodiazepines and barbiturates, ataxic effects more than sedative or motivational effects are implicated. However, for neuroleptics, loss of motivation or "anhedonia" better explains the decrease in operant responding. Differences between the main classes of psychotropic drugs but also within a class between 1,4 benzodiazepines or 1,5 benzodiazepines, hypnotic or nonhypnotic benzodiazepines, and typical or atypical neuroleptics are highlighted and correlated with human observations.

Animals↗

PubMed1990

Anxiolytic potential of sulpiride, clozapine and derivatives in the open-field test.

Recently acquired data question the sharp dichotomy between anxiolytics and neuroleptics, since disinhibitory effects have been measured in the rat with very low doses of haloperidol and higher doses of atypical neuroleptics in FI and DRL schedules, but also in the open-field test. That the DA transmission in certain brain regions is involved in some aspects of anxiety has recently been suggested. The present study confirms this hypothesis particularly with high doses of sulpiride (80 mg/kg) and clozapine (24 mg/kg) when tested in the open-field test. Moreover, the results show how a slight chemical modification of clozapine can give a direction to pharmacological activity with one derivative still resembling clozapine and the second one resembling haloperidol. As neuroleptics do not seem to influence the synthesis and utilization of GABA, the higher entry score observed with them would seem to depend above all on DA antagonism in the mesolimbic system.

Animals↗

PubMed1990

Effects of low doses of neuroleptics on temporal regulation in a differential reinforcement of response duration (DRRD) schedule in the dog.

It has been shown that low doses of neuroleptics could disinhibit behaviour in animals as well as in man. This study aims to measure the effects of low doses of haloperidol (0.01, 0.05, 0.1 mg/kg) and sulpiride (5, 10, 15 mg/kg) in the dog using a differential reinforcement of response duration (DRRD) schedule with positive and negative external stimuli. Together with a decrease in response rate, a leftward shift in the temporal distribution of response duration is measured. These results are discussed in terms of a deregulation of the internal clock, a lessening in the ability to wait for the reward, a reduction in the frustration of not obtaining reinforcements when errors are made and an increase in the sensibility to reinforcement through appetite stimulation or decrease in the satiety level.

Animals↗

PubMed1990

Clozapine: an atypical neuroleptic.

Since it was synthesized in 1960, much has been written about clozapine. Although a number of its properties are those of a neuroleptic, it displays marked differences from classical antipsychotics to the extent that it is currently listed as an atypical neuroleptic. A classical neuroleptic has been defined in man according to its antipsychotic properties, accompanied by extrapyramidal effects, and in animals according to its cataleptic properties, its ability to antagonize apomorphine and amphetamine stereotypies and to suppress the conditioned avoidance response. Moreover, the classical neuroleptic exerted depressive and anhedonic effects in most conditioning schedules. With clozapine, most of these properties are no longer strictly in force to the point that they call in question the validity of the tests carried out to detect the potential of neuroleptics. This article attempts to compare the characteristics of clozapine with those of classical neuroleptics from a toxicological, neuropharmacological, psychopharmacological and clinical point of view.

Animals↗

PubMedDate not supplied

Hypoxia-induced decrease of brain acetylcholine release detected by microdialysis.

The in-vivo extracellular release of acetylcholine (ACh) from the striatum of rats was measured by intracerebral microdialysis. The ACh levels were first estimated under normoxic conditions, after which the rats were exposed to either 10% or 5% oxygen for 1 h. The average ACh content was 2.9 pmol/20 min. During hypoxia, the ACh levels were decreased to 62% and 44% of the control value with 10% and 5% oxygen, respectively. The data confirmed the high sensitivity of the striatal cholinergic system to hypoxia. The results are discussed in relation to the hypothesis that disruption of Ca2+ homeostasis may underlie the hypoxia-induced deficits in ACh release.

Acetylcholine↗