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Biomedical subjects

H Matthies

Publications and source records attributed to H Matthies.

At least 73 records · Page 4Linked to original sources
PubMed1989

A simple procedure for the isolation of neurons from the CA1 and CA3 region of the postnatal rat hippocampus.

A procedure was developed for the isolation of pyramidal neurons from defined regions (CA1, CA3) of the postnatal rat hippocampus. By a quantitative approach the influence of various parameters (pO2,glucose, enzymes, temperature, buffers, [Ca++]0, mechanical isolation) was evaluated on number and state of viability of the isolated cells using the nigrosine exclusion test and considering the neurons' morphological features. Cell viability of disaggregated Ca1- and CA3-neurons was compared. These isolated neurons are well suited for whole-cell patch-clamp measurements as well as for pharmacological investigations.

Animals↗
PubMed1989

4-beta-phorbol-12,13-dibutyrate enhances K+-stimulated dopamine release from hippocampal slices.

Slices of rat hippocampus were labelled with [14C]dopamine, superfused continuously with oxygenated Krebs-Henseleit solution and stimulated with a potassium pulse (48 mM K+, 5 min.). 4-beta-phorbol-12,13-dibutyrate (PDB), an activator of protein kinase C (PKC), enhanced the potassium-evoked overflow of 14C. This effect was blocked by prior application of polymyxin B, a relatively selective inhibitor of PKC. In contrast, the PKC-inactive 4-alpha-phorbol-12,13-didecanoate (PDD) had no influence on the evoked transmitter overflow. The results suggest that PKC may also be involved in the regulation of hippocampal DA release. A possible link between PKC activation and DA release to processes of synaptic long-term potentiation is discussed.

Animals↗
PubMed1989

Domperidone, an inhibitor of the D2-receptor, blocks a late phase of an electrically induced long-term potentiation in the CA1-region in rats.

The influence of the D2-receptorblocker domperidone (DP) at a concentration of 1 microM was investigated on an electrically induced long-term potentiation (LTP) measured as the enhancement of the population spike (PS) amplitude in the hippocampal CA1. It could be shown that the drug does not influence the initiation but the maintenance of LTP. The results once again support the hypothesis that different phases of LTP exist which are realized by different cellular inputs.

Animals↗
PubMed1988

Orotate improves memory and enhances synaptic long-term potentiation in active avoidance behaviour in rats with perforant path stimulation as the conditioned stimulus.

Male Wistar rats were trained in an active avoidance task with stimulation of the perforant path with impulse trains of 15 Hz as the conditioning stimulus. Immediately after the first training session, methylglucamine orotate (225 micrograms), a memory improving drug, was injected intraventricularly. The retention of the learned behaviour was determined on the following day in a relearning session. Field potentials evoked in the dentate area by test stimuli from the perforant path electrode were recorded at different times after learning and relearning sessions to determine whether there were functional changes in the perforant path-granular cell synapses, which are involved in the conditioning pathway. Untreated control animals exhibited a so-called 'postconditioning potentiation', expressed as a long-lasting increase of both the excitatory postsynaptic potential (EPSP) and the population spike of the granular cells of the evoked test potentials. This finding reproduces previously published results. Methylglucamine orotate-treated rats showed significantly more conditioned reactions in the relearning sessions compared with untreated controls and a significantly more pronounced potentiation of the population spike, whereas the postconditioning potentiation of the field EPSP remained unaffected by the treatment. When both the control animals and the methylglucamine orotate-treated rats were divided into subgroups of good and poor learners according to their learning scores from the first training session, differences between the effect of the drug became evident. In good learners, the treatment with methylglucamine orotate after the learning session slightly, but significantly, improved retention compared with that of untreated good learners.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Inhibitors of calmodulin and protein kinase C block different phases of hippocampal long-term potentiation.

The effects of a calmodulin (CaM) inhibitor, which does not influence Ca2+ fluxes (calmidazolium, RO-24571), and a new potent inhibitor of protein kinase C (K-252b) on long-term potentiation (LTP) were compared in hippocampal slices. Tetanic stimulation of the stratum radiatum during perfusion of calmidazolium (50 nM) failed to induce the characteristic post-tetanic and long-term increase in the magnitude of CA1-evoked responses. During perfusion with K-252b (50 nM) post-tetanic potentiation and initial LTP is expressed normally, but thereafter declines back to baseline with a 60 min delay. By themselves, the inhibitors had no significant effect on synaptic transmission in a non-tetanized control input. Our data are in line with current evidence from several laboratories that CaM- and protein kinase C (PKC)-dependent processes are involved in LTP and support the hypothesis that CaM mediates initiation and that PKC mediates mechanisms underlying the maintenance of LTP.

Action Potentials↗
PubMed1988

Anisomycin, an inhibitor of protein synthesis, blocks late phases of LTP phenomena in the hippocampal CA1 region in vitro.

Long-term potentiation (LTP) with its extremely long duration has been frequently regarded as an elementary mechanism of information storage in the nervous system or at least as a suitable model for the study of mechanisms underlying functional plasticity and processes of learning and memory formation. Considering the necessity of an increased protein synthesis for memory consolidation and for the maintenance of LTP in granular synapses in vivo it was of interest to determine whether the LTP of the CA1 region of the hippocampus depends on protein synthesis as well. For the solution of this question anisomycin (ANI), a reversible blocker of protein synthesis, was used at a concentration of 20 microM, which blocked the [3H]leucine incorporation in hippocampal slices by at least 85%. It has been shown that in the CA1 region in vitro the maintenance of LTP (i.e. a late phase greater than 5 h) depends on an ongoing protein synthesis. A 3-h treatment with ANI immediately following multiple tetanization resulted in gradually developing loss of field excitatory postsynaptic potential (EPSP) and population spike (PS) potentiation (15 +/- 19% increase of the PS instead of the 96 +/- 14% increase in non-treated control experiments at the 8th h after tetanization). Furthermore, a late PS potentiation (greater than 6 h) of a second non-tetanized pathway to CA1 pyramidal cells has been observed (increase by 64 +/- 18% at the 8th h) for the first time. This potentiation was ANI-sensitive as well and suggests that the maintenance of LTP is dependent on a postsynaptic mechanism.

Action Potentials↗
PubMed1988

Polymyxin B, an inhibitor of protein kinase C, prevents the maintenance of synaptic long-term potentiation in hippocampal CA1 neurons.

The involvement of protein kinase C (PKC)-mediated processes in mechanisms of long-term potentiation (LTP) was suggested by recent studies which have demonstrated a correlation between PKC activation and LTP. However, it was not possible to tell whether there is a causal relationship between the two events. Therefore, we have examined the induction and maintenance of LTP in rat hippocampal slices in the presence of a relatively selective PKC inhibitor, using extracellular electrophysiological techniques. Bath application of 0.1-100 microM polymyxin B did not influence the occurrence of post-tetanic and long-term potentiation usually seen in test responses 1 and 10 min after a 100-Hz/1 s tetanic stimulation of stratum radiatum fibers. However, 20 microM polymyxin B significantly depressed the increase in population spike amplitude and population excitatory postsynaptic potential (EPSP) slope from 30 to 120 min onwards, following repeated tetanization. Immediately after the drug application only weak and reversible effects were seen by the same parameters in test responses of a non-tetanized control input. A late (greater than 6 h) heterosynaptic potentiation of the population spike in the control input was blocked by polymyxin B treatment. Whereas the EPSP-LTP was fully blocked, some potentiation of the population spike still remained, suggesting the independence of PKC of the additional spike (E/S) potentiation for the first 6 h. These results provide direct evidence that the PKC activation is not essential for the initial phase of LTP, but is a necessary condition for a medium and a late, protein synthesis-dependent phase in this monosynaptic pathway, i.e. for the maintenance of synaptic LTP.

Action Potentials↗
PubMed1988

Phorbol ester-induced hippocampal long-term potentiation is counteracted by inhibitors of protein kinase C.

As was shown previously (Reymann et al. 1988), the protein kinase C (PKC)-inhibitor polymyxin B prevents the maintenance of electrically induced long-term potentiation (LTP) of synaptic transmission to CA1 neurons, indicating that posttranslational phosphorylation processes mediated by PKC are involved in mechanisms underlying this form of synaptic plasticity. To make sure that 1.) the polymyxin B actually acts against PKC activation and 2.) the long-lasting potentiation elicited by phorbol esters (Malenka et al. 1986) is mediated by PKC-activation, we have tested polymyxin B as well as the potent PKC-inhibitor K-252b during phorbol ester-induced LTP. 4-beta-phorbol-12,13-dibutyrate (PDBu) - a known activator of protein kinase C, induces a remarkable potentiation at concentrations as low as 0.5 microM. When 20 microM polymyxin B or 40 nM K-252b was administered to rat hippocampal slices prior to such a weak phorbol ester treatment, this potentiation did not develop with the exception of a small increase in the population spike in spite of polymyxin B-treatment (42% instead of 120% increase at 2 h after PDBu). In contrast, spike potentiation induced by high concentrations of PDBu (10 microM) could not be counteracted by 100 microM polymyxin B. It is concluded that at low concentrations the phorbol ester-induced potentiation is mainly mediated by a selective activation of protein kinase C and that the prevented maintenance of electrically induced LTP by polymyxin B is in fact due to inhibition of this kinase. The spike potentiation developed faster than that of the EPSP raising the possibility that PDBu activates two separate PKC-dependent processes.

Action Potentials↗
PubMed1988

Alterations in calmodulin content in fractions of rat hippocampal slices during tetanic- and calcium-induced long-term potentiation.

The content of cytosolic and membrane-bound calmodulin was radioimmunologically determined in fractions of rat hippocampal slices 5 min to 7 hours after long-term potentiation (LTP) had been induced by tetanization or exposure of slices to 4 mM Ca++. In light of concepts presuming multistage dynamics in LTP development as reflecting different cellular mechanisms, similar patterns of calmodulin alterations were observed with both models: The alterations in calmodulin content occurred during the early phase(s) of LTP development and continued for two and one hours during tetanic- and calcium-induced LTP, respectively. Thus, 5-30 min after LTP elicitation, membrane-bound calmodulin increased while cytosolic calmodulin diminished and, inversely, 30 min later an increase in cytosolic and decrease in membrane-bound calmodulin were observed. Consequently, the present results indicate that calmodulin was involved in the early phases(s) of LTP development in terms of a two-step translocation sequence. Hence, calmodulin translocation within both intracellular compartments may reflect the involvement of Ca++-calmodulin-dependent intraneuronal metabolic processes which might induce and/or temporarily maintain neuronal functional changes occurring immediately after repeated or intense stimulation of synaptic functions.

Action Potentials↗
PubMed1988

Alterations in calmodulin and S-100 protein content of hippocampal slices during long-term potentiation.

The content of calmodulin and S-100 protein in fractions of rat hippocampal slices was assayed by solid phase radioimmunology and radial immunodiffusion, respectively. One hour after tetanization (electrical stimulation of area dentata granular cells and recording from CA3 pyramids) an inverse translocation of these Ca++-binding proteins was observed: an increase in the calmodulin content in the water-soluble and a decrease in the Lubrol-soluble fractions, while an increase in S-100 protein in the Triton-soluble and a decrease in the water-soluble fractions occurred. The results are suggestive of a regulatory function of these proteins in events during repetitive stimulation of a synaptic input. The calmodulin increase in the cytosolic compartment may reflect the involvement of Ca++-calmodulin dependent intraneuronal metabolic processes underlying the induction and/or temporary maintenance of neuronal functional changes occurring after repeated or intense synaptic activity. The elevated S-100 protein level in the membrane compartment might be interpreted in terms of functionally induced redistribution in that neuronal cells are provided with additional amounts of S-100 protein originating from the surrounding glial cells which store large amounts of soluble S-100 protein.

Animals↗
PubMed1988

A biochemical and immunohistological study of calmodulin in rat brain structures.

Calmodulin content and immunoreactivity in rat brain structures, believed to be essential site involved in plasticity events, were determined by using biochemical and immunohistochemical methods, respectively. The levels of cytosolic and membrane-bound calmodulin paralleled the overall distribution pattern of calmodulin immunoreactivity. Very intense immunoreactivity was observed in neuronal structures of hippocampus, striatum and mesencephalon. White matter structures and, especially, myelinated nerve fibres did not reveal calmodulin immunoreactivity. Thus, the present findings are consistent with data reported in the literature that calmodulin, unlike to other calcium-binding proteins, is primarily associated with neuronal elements. The present findings support the usefulness of calmodulin studies in elucidating of cellular mechanisms underlying neuronal plasticity.

Animals↗
PubMed1988

Different effects of 2-deoxy-sugars on memory formation.

When rats were trained on a brightness discrimination task, intrahippocampal injections of 2-deoxy-galactose interfered with long-term memory formation while galactose and 2-deoxy-glucose were ineffective altogether. No differences were found in the morphology of hippocampal CA1 neurons investigated light-microscopically after application of the sugars. The amnestic action of 2-deoxy-galactose is discussed in the light of a rather specific interference with fucosylation of proteoglycans involved in mechanisms underlying the formation of a memory trace.

Animals↗
PubMed1988

Alterations in calmodulin content of rat brain areas after chronic application of haloperidol and amphetamine.

The water-soluble (cytosolic) and Lubrol-soluble (membrane-bound) calmodulin contents were determined radioimmunologically in fractions of striatum, hippocampus and cerebellum of dopamine supersensitive rats. Development of supersensitivity was the sequel of 3-weeks treatment of the animals with 1 mg/kg haloperidol or 5 mg/kg amphetamine i.p. daily. In the dopamine-rich striatum, the membrane-bound calmodulin content was increased by both modes of treatment, consistent with data from the literature. The patterns suggest that additional calmodulin was synthesized under the conditions studied. The hippocampus, the region poor in dopamine while playing an essential role in learning and memory formation processes, revealed similar patterns after both modes of treatment. However, in this region a pronounced translocation was seen, i.e. a redistribution from the cytosolic into the membrane compartment, without signs evidencing enhanced synthesis. The third region under investigation, the cerebellum, did not show any alterations in calmodulin content. Differentiation between pre- and postsynaptic changes was not possible. The results are discussed in the light of the present knowledge about participation of dopaminergic systems in processes of neuronal plasticity.

Amphetamine↗
PubMed1988

Methylglucamine orotate does not affect dopamine-stimulated fucosylation of rat hippocampal proteins.

The present paper is concerned with the question whether dopamine-stimulated fucosylation of glycoproteins of the rat hippocampus in vitro is augmented by treating animals with methylglucamine orotate (MGO). Dopamine (DA) in concentrations between 0.1-0.5 mM resulted in a dose-dependent increase in L-fucose incorporation of up to about 130%. Neither the acute intraperitoneal application of 225 mg MGO/kg body mass nor the daily treatment of rats with 225 mg MGO/kg body mass over a 10-day period changed this dose-dependent relationship significantly. Even the in vitro substitution of nucleotides (1 mM) such as uridine 5'-monophosphate, cytidine 5'-monophosphate, guanosine 5'-monophosphate, and adenosine 5'-monophosphate did not alter dopamine-stimulated fucosylation of rat hippocampal proteins. These findings suggest that DA-stimulated fucosylation of brain proteins is not limited by the supply of nucleotides.

Animals↗
PubMed1988

Metabolism of D-proline beta-casomorphin derivatives in the rat brain.

The aim of the present study was to evaluate the metabolic breakdown of two biologically active derivatives of beta-casomorphin (beta CM)-i.e. D-proline4-beta CM (D-Pro4-beta CM) and des-tyrosine 1-D-proline4-beta CM (DT-D-Pro4-beta CM)- in the rat brain. After intracerebroventricular (icv.) administration of 0.78 nmoles of both [3H]D-Pro4-beta CM and [3H]DT-D-Pro4-beta CM, the concentration of the intact peptides and their metabolites was estimated in brain stem and corpus striatum. Both peptides were degraded in brain tissue forming a common metabolite. Phe-D-Pro-Gly. The metabolic half-lives of DT-D-Pro4-beta CM in brain stem and c. striatum were 22.6 min and 28.6 min, whereas those of D-Pro4-beta CM were 7.8 min and 8.2 min, respectively. According to both half-lives of the intact peptide and the kinetics of the formation of the stable metabolite Phe-D-Pro-Gly. DT-D-Pro4-beta CM seemed to be more resistant to biological degradation in brain tissue than D-Pro4-beta CM. In the case of D-Pro4-beta CM, the dipeptidylpeptidase IV (DP IV) (EC 3.4.14.-) is presumed to be the cardinal enzyme for the breakdown. Since the degradation of these peptides in brain tissue results in the unique metabolite Phe-D-Pro-Gly, the differences in the pattern of biological activities between D-Pro4-beta CM and DT-D-Pro4-beta CM may be due to the action of the corresponding intact peptide.

Animals↗
PubMed1988

Does avoidance learning only depend on mossy fiber distribution?

Rats and mice with a poor active avoidance behavior in the shuttle box exhibit a larger extent of the zone innervated by mossy fibers in the infrapyramidal area of the hippocampal sector CA3. The question arose whether only these differences in the amount of inputs from granular cells do correlate with poor avoidance learning, or whether cholinergic septal inputs are likewise related to behavioral performance. Inbred and non-inbred rats with low and high avoidance scores were used. Freezing sections were alternately used for TIMM-staining and for the histochemical visualization of the acetylcholinesterase activity. In comparison with "good avoidance learners" the rats with "poor active avoidance performance" exhibited a larger zone of mossy fibers and a lower activity of acetylcholinesterase in the investigated field. A significant inverse correlation between mossy fiber innervation and cholinergic septal inputs could be established. Our findings suggest that poor avoidance learning does not simply depend on mossy fiber distribution but seems to be dependent rather on the relation between mossy fiber innervation and cholinergic septal inputs.

Acetylcholinesterase↗