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1

Impact of sensory learning GABA-ergic tonic inhibition in mouse barrel cortex

100%
Mozrzymas J., Urban-Ciecko J.
Acta Neurobiologiae Experimentalis
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2009
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tom 69
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nr 3
Sensory learning is known to affect neuronal function, morphology and synaptic connectivity. It has been shown that various forms of classical conditioning involving whisker stimulation induce morphological changes in respective barrels (altered expression of GABAARs, NMDARs and GAD67). More recent studies have shown that sensory learning enhanced the inhibitory synaptic transmission (Tokarski et al. 2007). Our aim was to follow up the impact of sensory learning on GABAergic currents in the barrel cortex by addressing the issue of tonic GABAergic inhibition. We have characterized the tonic currents in naive mice for different cell types (Regular Spiking, Regular Spiking Non-Pyramidal and Fast Spiking) and found that the values of currents are correlated with the neuronal cell type. Interestingly, classical conditioning (tactile whisker stimulation associated with electric foot shock) affected the value of tonic current in the cell specifi c manner. To further explore the underlying mechanisms, we have used a specifi c “superagonist” (THIP) for δ-subunit containing GABAA receptors. Our data indicate that observed here impact of sensory learning on tonic currents results from altered responsiveness of δ-subunit containing receptors. In conclusion, we provide evidence that behavioral training does affect the tonic inhibition in the barrel cortex. Supported by the Ministry of Science and Higher Education grants PBZ/ MNiSW/07/2006/02 and N401 028 32/0664.
2

Culture conditions severely alter the proportions between GABA-and glutamate-evoked currents in hippocampal pyramidal neurons

81%
Szczot M., Wojtowicz T., Mozrzymas J.
Acta Neurobiologiae Experimentalis
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2009
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tom 69
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nr 3
Cultured hippocampal cells are commonly used as a convenient model but non-physiological conditions (impaired homeostasis, lack of glial cells etc.) persisting over long period of time raise concerns. Acute brain slices are believed to better maintain the physiological features but are often problematic for technical reasons (e.g. complicated access to neurons, attenuated spread of pharmaceutics). Non-physiological conditions in cell cultures during maturation of GABAergic and glutamatergic systems may alter expression of GABAA and glutamate receptors affecting thus the excitation to inhibition balance. Proportion between GABA and glutamate receptors may be evaluated by determining ratio between amplitudes of current responses to saturating agonist concentrations. We have recorded current responses to ultrafast applications of saturating GABA and glutamate concentrations in hippocampal cell cultures (9–15DIV) and in brain slices from CA1 pyramidal neurons of P19–P23 rats. For cell cultures, GABAergic and glutamergic currents ratio was 2.34 ± 0.45 (n=12) while for the brain slices it was only 0.24 ± 0.02 (n=5). These results provide evidence that non-physiological conditions in cell cultures may cause a dramatic change in expression pattern of GABAA and glutamate receptors. The underlying mechanisms are not known, but we may hypothesize that a homeostatic modulation due accumulation of neurotransmitters in culture medium could be involved. Support: grant no. 070231/Z/03/Z.
3

Does collagenase influence the biophysical properties of acetylcholine receptors channels?

81%
Mozrzymas J., Lorenzon P., Kwiecien R., Ruzzier F.
Biophysics of Membrane Transport
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1990
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tom 10
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nr 2
4

Synaptic plasticity in barrel cortex is occluded by classical conditioning training and depends on the activity of metalloproteinases

81%
Lebida K., Urban-Ciecko J., Mozrzymas J.
Acta Neurobiologiae Experimentalis
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2011
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tom 71
|
nr S
It is well established that classical conditioning paradigms induce plastic changes in the mouse barrel cortex. In particular, tactile whisker stimulation paired with a tail shock affects GABAergic currents in the layer IV in the cell-specific manner. It is thus expected that sensory learning might affect the neuronal networks in the “trained” barrel, possibly altering its ability to express the synaptic plasticity. To test this possibility, we have compared the long-term potentiation (LTP) induction in “trained” barrels in slices from animals which underwent classical conditioning to that in corresponding barrels in control (yoked, pseudoconditioned) mice. To induce LTP, classical pairing protocol was used (stimulation - layer IV, current-clamp whole-cell recordings - layer II/III). Interestingly, while in control mice, pairing resulted in a clear LTP (161% EPSP increase, 30 min after pairing), in trained animals the LTP induction was nearly absent. This result suggests that behavioral learning occludes the synaptic plasticity in the considered model. It has been demonstrated in other brain region (hippocampus) that synaptic plasticity as well as behavioural learning may critically depend on the activity of metalloproteases (MMPs). We were thus interested whether LTP in the barrel cortex depends on these enzymes. To address this issue, pairing protocol was used to induce LTP in the barrel cortex of control animals and MMPs were blocked by a broad spectrum MMP inhibitor (FN-439). We found that pre-treatment of slices with MMPs inhibitor practically abolished LTP indicating that these enzymes play a critical role in the LTP maintenance in this model. In conclusion, these data indicate that behavioural learning occludes the synaptic plasticity in the barrel cortex and that LTP maintenance in this preparation relies on the activity of MMPs. Supported by the Ministry of Science and Higher Education grants N401 028 32/0664 and NN401541540.
5

Effect of matrix metalloprotease inhibition on short and long term plasticity of mossy fiber-CA3 synapses

61%
Wojtowicz T., Piotrowska A., Podborska-Okolow M., Dziegiel P., Kaczmarek L., Mozrzymas J.
Acta Neurobiologiae Experimentalis
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2009
|
tom 69
|
nr 3
Matrix metalloproteinases (MMPs) are a large family of extracellularly-acting endopeptidases. MMPs were shown to play an important role in hippocampal plasticity phenomena such as LTP, learning and memory. In particular, in Shaffer collateral/ CA1 (Sch/CA1) synapses, MMPs are crucial for maintenance of long term plasticity requiring NMDA receptor (NMDAR) activation. However, it is not known whether MMPs affect plastic changes in mossy-fi ber/CA3 (mf/CA3) synapses, where LTP is basically presynaptic and NMDAR-independent. Field potential (fEPSPs) recordings in CA3 region (mf stimulation) revealed no effect of FN439 (panmetalloprotease inhibitor) on the short-term plasticity but the late phase of LTP was abolished by this agent similar to Sch/CA1 pathway. Since maintenance of LTP in Sch/CA1 was specifi cally dependent on MMP-9 activity, we have performed immunostaining for MMP-9 in mf/CA3 pathway. Semi-quantitative analysis revealed that induction of LTP resulted in several fold increase in MMP-9 immunoreactivity within hilar and CA3 region relative to control slices. We conclude that MMPs are crucial for long- but not short-term plasticity in mf/CA3 synapses and that LTP induction in this pathway is accompanied by a robust increase in MMP-9 immunoreactivity. It seems thus that consolidation phase of LTP is critically dependent on MMP activity in the two major hippocampal pathways (Sch/CA1 and mf/CA3) where LTP induction mechanisms show profound differences. Support: Grant No. P-N/030/2006.
6

STIM1, STIM2 and Orai1-overexpression of key store operated calcium entry in transgenic mice brain

61%
Majewski L., Wiera G., Wojtowicz T., Boguszewski P. M., Mozrzymas J., Kuznicki J.
Acta Neurobiologiae Experimentalis
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2015
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tom 75
|
nr Supl.
BACKGROUND AND AIMS: Alzheimer’s disease (AD) is the most common age-related neurodegenerative disorder. At least two types of AD can be distinguished: sporadic AD (SAD) of unknown etiology, which accounts for most cases, and genetically encoded familial AD (FAD), which affects up to 5% of all patients. Altered calcium homeostasis in neurons is proposed to be one of the early events responsible for AD. Disturbances in Ca2+ signaling are found in SAD patients before any obvious extracellular Aβ pathology; moreover, Ca2+ dysfunction augments Aβ formation and Tau hyperphosphorylation. One of the objectives of our present project is to understand how elevated basal Ca2+ level in neurons contributes to neurodegeneration. METHODS: Generation of transgenic mice using DNAmicroinjection technique. RESULTS: We have generated three transgenic mouse lines independently overexpressing,specifically in brain neurons, key proteins of SOCE – STIM1, STIM2 and Orai1. The phenotype of these mice is being analyzed by electrophysiology, behavior and Ca2+ imaging. Our group has shown that the cytoplasmic resting Ca2+ level in cultured neurons can be modulated by overexpression of STIM proteins, ER Ca2+ sensors involved in the Store Operated Calcium Entry (SOCE). We also detected the enhanced magnitude of Ca2+ influx during SOCE in human lymphocytes from SAD patients, and decreased level of STIM2 protein in human lymphocytes from FAD patients in parallel to an attenuation of SOCE. CONCLUSIONS: The obtained lines can be a suitable model to verify the hypothesis that brain dysfunction during ageing is induced by changes in Ca2+ homeostasis.
7

Fine - tuned MMP-9 level is critical for LTP maintenance in mossy fiber - CA3 hippocampal pathway

61%
Wiera G., Wojtowicz T., Chmielewska M., Wawrzyniak M., Kaczmarek L., Dziegiel P., Mozrzymas J.
Acta Neurobiologiae Experimentalis
|
2011
|
tom 71
|
nr S
Matrix metalloproteinases (MMPs) are a family of endopeptidases involved in degradation and turnover of extracellular matrix proteins. Among them, MMP-9 is implicated in learning and synaptic plasticity. We have shown using inhibitor FN-439 that MMPs play a critical role in LTP maintenance in the mossy fiber - CA3 hippocampal projection (Wójtowicz and Mozrzymas 2010). In the present study we address the specific role of MMP-9 in the plasticity of this pathway. Gel zymography revealed an up regulation of pro- and active form of MMP-9 in homogenates from slice fragments containing mf-CA3 projection, fixed 2 h after LTP induction. Interestingly, this effect was abolished when LTP was induced in the presence of protein synthesis inhibitor (cycloheximide). Moreover, the effects of cycloheximide and FN-439 on fEPSPs were indistinguishable for up to 2 h after LTP induction. Additionally, we observed on western blot a significant decrease in 30 kDa β-dystroglycan digestion product 2 hours after LTP induction. To further explore the mechanism of MMP-9 action, LTP was induced in slices from MMP-9-/- and MMP-9 overexpressing rodents. In slices from KO mice, the late phase of LTP was severely impaired, although not abolished (136% vs. 189% in WT). Surprisingly, in slices from MMP-9 overexpressing rats, LTP was impaired in a similar manner as in KO mice (113% vs. 171%). Moreover, in MMP-9 overexpressing rats, LTP induction was accompanied by increase in MMP-9 level (shown by gel zymography) similar to what was observed in WT rats. These results indicate that fine-tuned MMP-9 balance is critical for LTP consolidation in mf-CA3 pathway, as in the absence of MMP-9 or in conditions of its excess, LTP is impaired. These results may raise a possibility that impairment of optimal MMP-9 activity (implicated in schizophrenia or bipolar mood disorder) may be detrimental for cognitive processes. Supported by Ministry for Science and Higher Education grants PN/030/2006 and N N401 541540.
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