Search PubMed⌕ Search

Biomedical subjects

M Tetas

Publications and source records attributed to M Tetas.

11 recordsLinked to original sources
PubMed2000

Copper sensitivity in dorsal hippocampus slices.

The action of copper on the pyramidal neurons in CA1 of the hippocampus is little understood. Our main aim was to study the possible interaction of copper on the synaptic network in CA1 pyramidal neurons. We used Wistar rats hippocampus slices in a recording chamber. The population response ("population of spikes") collected by an extracellular micropipette under baseline conditions served as control. Copper, GABA, bicuculline and picrotoxin were delivered in different experimental conditions to the slice. One, 10 and 100 microM of copper concentration decreased significantly the amplitude and duration of the population spikes in relation to the control response. This effect did not show concentration dependency. Copper in bicuculline medium decreased significantly the duration response in relation to the control response and in relation to copper effect in a free bicuculline medium. This phenomenon emphasizes the copper action on the GABA (B) and (C) receptors. Copper in a picrotoxin medium increased significantly the excitability of the response. This new effect suggests that copper acts on non-GABA receptors, an effect that could be detected when the GABA receptors were inactivated. As a result of these findings it appears that, under our experimental conditions, copper generated transient sensitivity changes in pyramidal neurons of CA1 dorsal hippocampus.

Action Potentials↗
PubMed1995

Behavioral effects evoked by SKF 38393 and LY 171555 in adult cats.

The aim of the present work was to study the behavioral effects elicited in adult cats by the selective D1 agonist, SKF 38393, and the D2 agonist, LY 171555, comparing their effects with those evoked by apomorphine. In 10 adult cats, 0.5, 1.0, 4.0, and 8.0 mg/kg IP of SKF 38393 were administered at random. A dose-response effect was observed related to alertness, indifference, and locomotion. The overall effect of SKF 38393 was inhibitory. To the same 10 animals, LY 171555 in doses of 0.25, 0.5, and 1.0 mg/kg were injected IP. This drug had an excitatory and more complex effect than what was observed with the D1 agonist. Increases in locomotion, in alertness, indifference, fear, olfaction, pupillary dilation, hallucination, limb flicking, and head shaking were recorded. Apomorphine given to the same cats, in a dose equimolar to 1.0 mg/kg of LY 171555, elicited behaviors that resembled those elicited by the latter drug, but of a lesser intensity and duration. The interval between the different treatments was approximately 2 months. These results show clearly that the D2 receptor is the main dopaminergic receptor involved in the mechanism of production of most of the behavioral effects produced by some of the dopaminergic agonist drugs like apomorphine.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1995

Effects of naloxone on the behaviors evoked by amphetamine and apomorphine in adult cats.

1. This work was undertaken in order to study whether the opioid system is involved in the modulation of the behaviors induced by two agonists of the dopaminergic system, amphetamine and apomorphine in adult cats. 2. Naloxone, an antagonist of the mu, delta and kappa opioid receptors was administered to twelve female mongrel cats; 0.5, 1.0 and 2.0 mg/kg s.c. were injected in order to analyse its own effect of naloxone. This drug produced NREMs behavior and accordingly the cat showed an overall decrease of its activities. 3. Amphetamine (2.5 mg/kg s.c.) and apomorphine (2.0 mg/kg s.c.) were injected before and after naloxone administration (2.0 mg/kg s.c.), in separate sessions. 4. The behaviors recorded were compared. Some of the behaviors showed modifications both with amphetamine (inappetence was increased and locomotion decreased) and apomorphine (indifference and inappetence increased; locomotion and olfaction decreased). 5. These changes were considered as consequence of the NREMs behavior induced by naloxone and not as a result of a modulation by the opioid system of the activation of the dopaminergic system elicited by amphetamine and apomorphine. Regarding the mechanism of NREMs induced by naloxone probably the dopaminergic, noradrenergic and GABAergic systems may be involved.

Amphetamine↗
PubMed1994

Comparative analysis of the behaviors evoked by bromocriptine and quinpirole (LY 171555) in adult cats.

The aim of this work was to compare the behavioral effects of bromocriptine and quinpirole, two agonists of the D-2 dopaminergic receptor, either injected alone or combined with the D-1 dopaminergic receptor, SKF 38393. In ten adult mongrel cats the following experimental series were carried out: i) a dose-response study with bromocriptine administering 0.5-1.0-4.0 and 8.0 mg/kg s.c.; ii) a behavioral study injecting 4.0 mg/kg of bromocriptine plus 2.0 mg/kg of SKF 38393; iii) the same analysis administering 0.5 mg/kg of LY 171555 plus 1.0 mg/kg of SKF 38393, compared with the same dose of LY 171555 plus 4.0 mg/kg of SKF 38393; iv) an analysis of the behavioral effects of 8.0 mg/kg of bromocriptine compared with 1.0 mg/kg of quinpirole. The main findings were: i) bromocriptine injected, in four different doses evoked decrease in locomotion, and increase in indifference, inappetence, pupillary dilation and limb flicks; ii) the combined administration of 4.0 mg/kg of bromocriptine plus 2.0 mg/kg of SKF 38393 did not elicit behavioral changes different to those produced by bromocriptine alone; iii) quinpirole (1.0 mg/kg) evoked more intense behaviors than bromocriptine (8.0 mg/kg); iv) comparing quinpirole injected alone with the combination of quinpirole plus SKF 38393, this latter treatment produced more intense behaviors than the former. It is concluded: i) SKF 38393 potentiates the behavioral effects produced by quinpirole; this potentiation was not found when bromocriptine was combined with SKF 38393 and ii) the more intense behavioral effect elicited by quinpirole compared with bromocriptine may be explained by the fact that the latter drug is a selective D-2 agonist, whereas the former one is an agonist of the D-2 and the D-3 receptors.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1993

Effects of SCH 23390 and sulpiride on the behaviors evoked by amphetamine and apomorphine in adult cats.

1. The aim of the present study was to analyze whether the dopaminergic D1 and D2 receptors are involved in the production of the behaviors evoked by parenteral administration of amphetamine and apomorphine in adult cats. 2. Fifteen mongrel cats of both sexes were injected, in separate sessions, with 2.5 mg/kg of amphetamine and 2.0 mg/kg of apomorphine. The D1 receptor blocker, SCH 23390 was administered (0.3 mg/kg i.p.) and after 60 min, amphetamine and apomorphine were again injected on different days. The same procedure was carried on with sulpiride in two doses (20 and 30 mg/kg i.p.). The behaviors induced by the two dopaminergic drugs, before and after the receptor blocker administration were respectively compared. The Wilcoxon signed rank test was employed for statistical analysis. Three independent observers recorded the behaviors. 3. SCH 23390 and sulpiride produced per se hypomotility and sedation, effects that were considered when analysing the results. Some of the behaviors produced by amphetamine (pupillary dilation, head movements) were slightly modified by both receptor blockers. SCH 23390 only modified the licking behavior produced by apomorphine. In contrast, sulpiride blocked almost all the behaviors elicited by apomorphine, especially when the 30 mg/kg dose was administered. It is concluded that the behaviors produced by the 2 mg/kg dose of apomorphine are evoked by its binding to the post-synaptic dopaminergic D2 receptors and blocked by sulpiride.

Amphetamine↗
PubMed1992

Cholinergic blockade with scopolamine in adult cats. Effects on the behaviors evoked by apomorphine and amphetamine.

1. The aim of this work is to analyse the role that the cholinergic system could play in the production of the behaviors evoked by apomorphine and amphetamine in adult cats. These two drugs were injected s.c. in separate sessions, before and after a s.c. administration of scopolamine which blocked the muscarinic receptors. The pre and post-scopolamine results of the behaviors produced by the two catecholaminergic drugs were compared using the non-parametric Wilcoxon signed rank test. 2. In a previous step a dose-response study of the behavioral effects of scopolamine, in doses of 0.05, 0.1, 0.4 and 0.8 mg/kg was carried out in ten cats. The Kruskal-Wallis and the non-parametric multiple comparison tests were employed. A dose-dependent decrease in motility (locomotion) and a dose-dependent increase in inappetence and pupillary dilation were found. 3. In thirteen cats which were injected with 2 mg/kg of apomorphine and 2.5 mg/kg of amphetamine the findings were: 1--apomorphine after scopolamine produced a decrease in the hypermotility, compared with the results observed with the former drug previous to scopolamine; 2--with amphetamine an increase in immobility and a decrease in indifference were observed. 4. The authors conclude that the decrease in motility recorded with apomorphine and amphetamine after scopolamine, could be attributed to the proper effect of scopolamine. No explanation could be found for the decrease in indifference found by injecting amphetamine after scopolamine. 5. Considering the antagonistic effect between the dopaminergic and the cholinergic systems and that the latter one has an arousal effect, we postulate that the behavioral indifference produced by apomorphine and amphetamine could be the result of a kind of blockade of the cholinergic system when the catecholaminergic system is activated through the administration of the two cited drugs.

Amphetamine↗
PubMed1992

Effects of disulfiram, phenoxybenzamine and propranolol on the behaviors evoked by apomorphine and amphetamine in adult cats.

The aim of this work was to study the role that the noradrenergic system could play in the mechanism of production of the behaviors evoked by parenteral injection of apomorphine and amphetamine in adult cats. Ten cats were injected s.c. with 2 mg/kg of apomorphine and 2.5 mg/kg of amphetamine in separate sessions. The behaviors were recorded, until control conditions were again attained. In a second stage, disulfiram was administered ip., followed by apomorphine and amphetamine in the same doses as cited above. The effects on behaviors produced by disulfiram and those of apomorphine and amphetamine were recorded by three independent observers. Comparisons of the pre- and post-disulfiram behavioral results were analyzed with the help of the non-parametric Wilcoxon signed rank test. In another group of ten cats a similar procedure was carried on employing the alpha and beta noradrenergic blocking agents, phenoxybenzamine and propranolol. The noradrenergic blocking drugs, especially disulfiram and phenoxybenzamine produced by themselves a decrease in motility, in alertness and an increase in indifference and inappetence. Apomorphine and amphetamine administered after the blocking drugs showed slight behavioural modifications, reflection most of them the changes produced by the three blocking drugs. It is concluded that probably the nor-adrenergic system could be involved in the hypomotility elicited by amphetamine. NA is not involved in the induction of the other behaviors evoked by apomorphine and amphetamine.

Amphetamine↗
PubMed1988

[Hematopoietic microenvironment: cellular and extracellular matrix elements].

In bone marrow, cellular stroma together with extracellular matrix (EM) provide an adequate microenvironment for the proliferation and differentiation of hemopoietic progenitor cells. In this article we describe studies on the cell characteristics of a main stromal phenotype, a fibroblast-like cell and its ability to produce in vitro EM components. Comparative studies were performed in fibroblast cultures derived from normal and acute lymphoblastic leukemic (ALL) bone marrow. The grow characteristics of fibroblasts from ALL marrow as well as its capacity to synthetize collagen, fibronectin and GAGs are impaired when compared to fibroblast from normal marrow. Thus, in ALL the impaired production of EM biomolecules by a transient damaged population of stromal cells, may contribute to the development of a defective microenvironment for hemopoiesis.

Bone Marrow Cells↗