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Aim: Striatin (Strn) is a scaffold protein expressed in cardiomyocytes (CMs) and alteration of its expression are described in various cardiac diseases. However, the alteration underlying its pathogenicity have been poorly investigated. Methods: We studied the role(s) of cardiac Strn gene (STRN) by comparing the functional properties of CMs, generated from Strn‐KO and isogenic WT mouse embryonic stem cell lines. Results: The spontaneous beating rate of Strn‐KO CMs was faster than WT cells, and this correlated with a larger fast INa conductance and no changes in If. Paced (2–8 Hz) Strn‐KO CMs showed prolonged action potential (AP) duration in comparison with WT CMs and this was not associated with changes in ICaL and IKr. Motion video tracking analysis highlighted an altered contraction in Strn‐KO CMs; this was associated with a global increase in intracellular Ca2+, caused by an enhanced late Na+ current density (INaL) and a reduced Na+/Ca2+ exchanger (NCX) activity and expression. Immunofluorescence analysis confirmed the higher Na+ channel expression and a more dynamic microtubule network in Strn‐KO CMs than in WT. Indeed, incubation of Strn‐KO CMs with the microtubule stabilizer taxol, induced a rescue (downregulation) of INa conductance toward WT levels. Conclusion: Loss of STRN alters CMs electrical and contractile profiles and affects cell functionality by a disarrangement of Strn‐related multi‐protein complexes. This leads to impaired microtubules dynamics and Na+ channels trafficking to the plasma membrane, causing a global Na+ and Ca2+ enhancement. [ABSTRACT FROM AUTHOR]

In this study, we have addressed the issue of neural circuit formation using the mouse spinal cord as a model system. Our primary objective was to assess the suitability of organotypic cultures from embryonic mouse spinal cord to investigate, during critical periods of spinal network formation, the role of the local spinal cellular environment in promoting circuit development and refinement. These cultures offer the great advantage over other in vitro systems, of preserving the basic cytoarchitecture and the dorsal-ventral orientation of the spinal segment from which they are derived [Eur J Neurosci 14 (2001) 903; Eur J Neurosci 16 (2002) 2123]. Long-term embryonic spinal cultures were developed and analyzed at sequential times in vitro, namely after 1, 2, and 3 weeks. Spatial and temporal regulation of neuronal and non-neuronal markers was investigated by immunocytochemical and Western blotting analysis using antibodies against: a) the non-phosphorylated epitope of neurofilament H (SMI32 antibody); b) the enzyme choline acetyltransferase, to localize motoneurons and cholinergic interneurons; c) the enzyme glutamic acid decarboxylase 67, to identify GABAergic interneurons; d) human eag-related gene (HERG) K+ channels, which appear to be involved in early stages of neuronal and muscle development; e) glial fibrillary acidic protein, to identify mature astrocytes; f) myelin basic protein, to identify the onset of myelination by oligodendrocytes. To examine the development of muscle acetylcholine receptors clusters in vitro, we incubated live cultures with tetramethylrhodamine isothiocyanate-labeled α-bungarotoxin, and we subsequently immunostained them with SMI32 or with anti-myosin antibodies. Our results indicate that the developmental pattern of expression of these markers in organotypic cultures shows close similarities to the one observed in vivo. Therefore, spinal organotypic cultures provide a useful in vitro model system to study several aspects of neurogenesis, gliogenesis, muscle innervation, and synaptogenesis. [Copyright &y& Elsevier]

Aim: Striatin (Strn) is a scaffold protein expressed in cardiomyocytes (CMs) and alteration of its expression are described in various cardiac diseases. However, the alteration underlying its pathogenicity have been poorly investigated., Methods: We studied the role(s) of cardiac Strn gene (STRN) by comparing the functional properties of CMs, generated from Strn-KO and isogenic WT mouse embryonic stem cell lines., Results: The spontaneous beating rate of Strn-KO CMs was faster than WT cells, and this correlated with a larger fast I Na conductance and no changes in I f . Paced (2-8 Hz) Strn-KO CMs showed prolonged action potential (AP) duration in comparison with WT CMs and this was not associated with changes in I CaL and I Kr . Motion video tracking analysis highlighted an altered contraction in Strn-KO CMs; this was associated with a global increase in intracellular Ca 2+ , caused by an enhanced late Na + current density (I NaL ) and a reduced Na + /Ca 2+ exchanger (NCX) activity and expression. Immunofluorescence analysis confirmed the higher Na + channel expression and a more dynamic microtubule network in Strn-KO CMs than in WT. Indeed, incubation of Strn-KO CMs with the microtubule stabilizer taxol, induced a rescue (downregulation) of I Na conductance toward WT levels., Conclusion: Loss of STRN alters CMs electrical and contractile profiles and affects cell functionality by a disarrangement of Strn-related multi-protein complexes. This leads to impaired microtubules dynamics and Na + channels trafficking to the plasma membrane, causing a global Na + and Ca 2+ enhancement., (© 2024 The Authors. Acta Physiologica published by John Wiley & Sons Ltd on behalf of Scandinavian Physiological Society.)

Primary neuronal culture from rodents is a well-established model to investigate cellular neurobiology in vitro . However, for this purpose cell cultures need to be generated expressly, requiring extensive animal handling. Furthermore, often the preparation of fresh culture generates an excess of cells that are ultimately wasted. Therefore the ability to successfully cryopreserve primary neural cells would represent an important resource for neuroscience research and would allow to significantly reduce the sacrifice of animals. We describe here a novel freezing medium that allows long-term cryopreservation of primary mouse neurons prepared from E15.5 embryos. Combining imaging, biochemical and electrophysiological analyses, we found that cryopreserved cultures are viable and mature regarding morphology and functionality. These findings suggest that cryopreserved neurons are a valuable alternative to acutely dissociated neural cultures.

In rats, iron deficiency produces an alteration in myelin formation. However, there is limited information on the effects of this condition on oligodendroglial cell (OLGc) proliferation and maturation. In the present study, we further analyzed the hypomyelination associated with iron deficiency by studying the dynamics of oligodendrogenesis. Rats were fed control (40 mg Fe/kg) or iron-deficient (4 mg Fe/kg) diets from gestation day 5 until postnatal day 3 (P3) or 11 (P11). OLGc proliferation, migration and differentiation were investigated before and after an intracranial injection of apotransferrin at 3 days of age (P3). The proliferating cell population was evaluated at P3. Iron-deficient (ID) animals showed an increase in the oligodendrocyte precursors cell (OPC) population in comparison with controls. The overall pattern of migration of cells labeled with BrdU was investigated at P11. Iron deficiency increased the amount of BrdU(+) cells in the corpus callosum (CC) and decreased OLGc maturation and myelin formation. Changes in nerve conduction were analyzed by measuring visual evoked potentials. Latency and amplitude were significantly disturbed in ID rats compared with controls. Both parameters were substantially normalized when animals were treated with a single intracranial injection of 350 ng apotransferrin (aTf). The current results give support to the idea that iron deficiency increases the number of proliferating and undifferentiated cells in the CC compared with the control. Treatment with aTf almost completely reverted the effects of iron deficiency, both changing the migration pattern and increasing the number of mature cells in the CC and myelin formation.

Adducins are a family of proteins found in cytoskeleton junctional complexes, which bind and regulate actin filaments and actin-spectrin complexes. In brain, adducin is expressed at high levels and is identified as a constituent of synaptic structures, such as dendritic spines and growth cones of neurons. Adducin-induced changes in dendritic spines are involved in activity-dependent synaptic plasticity processes associated with learning and memory, but the mechanisms underlying these functions remain to be elucidated. Here, beta-adducin knockout (KO) mice were used to obtain a deeper insight into the role of adducin in these processes. We showed that beta-adducin KO mice showed behavioral, motor coordination and learning deficits together with an altered expression and/or phosphorylation levels of alpha-adducin and gamma-adducin. We found that beta-adducin KO mice exhibited deficits in learning and motor performances associated with an impairment of long-term potentiation (LTP) and long-term depression (LTD) in the hippocampus. These effects were accompanied by a decrease in phosphorylation of adducin, a reduction in alpha-adducin expression levels and upregulation of gamma-adducin in hippocampus, cerebellum and neocortex of mutant mice. In addition, we found that the mRNA encoding beta-adducin is also located in dendrites, where it may participate in the fine modulation of LTP and LTD. These results strongly suggest coordinated expression and phosphorylation of adducin subunits as a key mechanism underlying synaptic plasticity, motor coordination performance and learning behaviors.

Alzheimer's disease is a neurodegenerative disorder characterized by neuronal loss associated with a progressive impairment of cognitive functions. Early consequences of Alzheimer's disease include deficit of cholinergic signalling in particular regions controlling memory processes, such as the cortex and hippocampus, and accumulation of beta-amyloid (Abeta) peptide in neuritic plaques. The cholinergic system depends for its integrity and function on nerve growth factor. Chronic nerve growth factor deprivation in transgenic mice (AD11) engineered to produce recombinant neutralizing anti-nerve growth factor antibodies leads to progressive age-dependent Alzheimer's-like neurodegenerative pathology similar to that found in patients with Alzheimer's disease, associated with a selective loss of cholinergic neurones in the basal forebrain. Here we show that in the hippocampus of 6-month-old AD11 mice, Abeta aggregates started appearing in the CA1 region. The accumulation of Abeta was associated with a loss of cholinergic function at CA3-CA1 synapses. Whereas in wild-type mice nicotine induced a persistent increase of synaptic efficacy via alpha7 nicotine acetylcholine receptors, in AD11 mice this alkaloid failed to modify synaptic strength. Moreover, nicotine failed to transiently enhance the frequency of spontaneous miniature glutamatergic currents (miniature excitatory postsynaptic currents) recorded from CA1 but not from CA3 pyramidal neurones of AD11 mice. However, in CA3 principal cells of AD11 mice, the potentiating effect of nicotine on miniature excitatory postsynaptic currents was prevented when Abeta peptide 1-42 was added to the extracellular solution. These data suggest that in AD11 mice, Abeta interferes with nicotine acetylcholine receptors at the level of presynaptic glutamatergic terminals, inhibiting their function possibly through calcium signalling via presynaptic alpha7 nicotine acetylcholine receptors.

The role of activity-dependent plasticity in modulating inhibitory synapses was investigated in embryonic rat spinal cord slice cultures, by chronic exposure to non-NMDA receptor blockers. GABAergic synaptic efficacy in control and chronic-treated cultures was investigated by patch-recordings from visually identified spinal interneurons. In both culture groups proximal stimulation induced the appearance of postsynaptic currents (PSCs), which were fully antagonized by 20 microM bicuculline application and reverse polarity at potential values close to those reported for spontaneous GABAergic PSCs. In chronically treated cells GABAergic evoked PSCs displayed a larger failure rate and a smaller coefficient of variation of mean PSC amplitude, when compared to controls. As opposed to controls, chronic GABAergic evoked PSCs did not facilitate upon paired-pulse stimulation. Facilitation at chronic synapses was observed when extracellular calcium levels were decreased below physiological values (< 2 mM). Kainate was used to disclose any functional differences between control and treated slices. In accordance with the presynaptic action of kainate, the application of this drug along with GYKI, an AMPA receptor selective antagonist, changed, with analogous potency, short-term plasticity of GABAergic synapses from control and treated cultures. Nevertheless, in chronic cultures, the downstream effects of such activation unmasked short-term depression. Ultrastructural analysis of synapses in chronically treated cultures showed a reduction both in symmetric synapses and in the number of vesicles at symmetric terminals. Thus, based on electrophysiological and ultrastructural data, it could be suggested that during the development of spinal circuits, GABAergic synapses are modulated by glutamatergic transmission, and thus implying that excitatory transmission regulates the strength of GABAergic synapses.

Generation of spontaneous rhythmic activity is a distinct feature of developing spinal networks. We report that rat embryo organotypic spinal cultures contain the basic circuits responsible for pattern generation. In this preparation rhythmic activity can be recorded from ventral interneurons and is developmentally regulated. When chronically grown in the presence of an AMPA/kainate receptor blocker, this circuit expresses long-term plasticity consisting largely of increased frequency of fast synaptic activity and reduction in slow GABAergic events. We examined whether, once this form of homeostatic plasticity is established, the network could still exhibit rhythmicity with properties similar to controls. Control or chronically treated ventral interneurons spontaneously generated (with similar probability) irregular, network-driven bursts over a background of ongoing synaptic activity. In control cultures increasing network excitability by strychnine plus bicuculline, or by raising [K(+)](o), induced rapid-onset, regular rhythmic bursts. In treated cultures the same pharmacological block of Cl(-)-mediated transmission or high-K(+) application also induced regular patterned activity, although significantly faster and, in the case of high K(+), characterized by slow onset due to postsynaptic current summation. Enhancing GABAergic transmission by pentobarbital surprisingly accelerated the high-K(+) rhythm of control cells (though depressing background activity), whereas it slowed it down in chronically treated cells. This contrasting effect of pentobarbital suggests that, to preserve bursting ability, chronic slices developed a distinct GABAergic inhibitory control on over-expressed bursting circuits. Conversely, in control slices GABAergic transmission depressed spontaneous activity but it facilitated bursting frequency. Thus, even after homeostatic rearrangement, developing mammalian spinal networks still generate rhythmic activity.

Bath application of compound T-588, a neuroprotective agent, reduced paired-pulse and repetitive-pulse facilitation at mammalian and crustacean neuromuscular junctions. In addition, it reduced voltage-gated sodium and potassium currents in a use-dependent fashion, but had only a small effect on the presynaptic Ca(2+) conductance. By contrast, it blocked FM 1-43 vesicular uptake but not its release, in both species. Postsynaptically, T-588 reduced acetylcholine currents at the mammalian junction in a voltage-independent manner, but had no effect on the crayfish glutamate junction. All of these effects were rapidly reversible and were observed at concentrations close to the compound's acute protective level. We propose that this set of mechanisms, which reduces high-frequency synaptic transmission, is an important contributory factor in the neuroprotective action of T-588.

1. The effects of different calcium channel blockers (omega-agatoxin IVA (omega-Aga IVA), omega-conotoxin GVIA (omega-CgTx GVIA) and dihydropyridines) were tested on spontaneous and evoked transmitter release at embryonic and newborn rat neuromuscular junctions (NMJs). 2. The nerve-evoked transmitter release quantal content (m) was strongly reduced by the P/Q-type voltage-dependent calcium channel (VDCC) blocker omega-Aga IVA (100 nM) at newly formed endplates of embryos and 0- to 11-day-old rats, in agreement with the effect of this blocker on transmitter release at mature and reinnervating muscles. 3. omega-CgTx GVIA (1-5 microM), the N-type VDCC blocker, also caused a significant reduction in m at newly formed NMJs early in development (embryos and 0- to 4-day-old rats), while it was ineffective in more mature animals (5- to 11-day-old rats). 4. L-type channel blockers, nitrendipine (1 microM) and nifedipine (1 microM), did not significantly affect neurally evoked release at developing NMJs. However, nifedipine (10 microM) was able to increase m significantly at 0- to 4-day-old rat NMJs. 5. At developing NMJs, K+-evoked transmitter release was dependent on Ca2+ entry through VDCCs of the P/Q-type family (100 nM omega-Aga IVA reduced 70 % of the K+-evoked miniature endplate potential frequency). N- and L-type VDCC blockers did not affect this type of release. 6. We conclude that at rat neuromuscular junctions the presynaptic calcium channel types involved in transmitter release undergo developmental changes during the early postnatal period.

1. The effects of the voltage-dependent calcium channel (VDCC) blockers omega-agatoxin IVA (omega-AgaIVA), omega-conotoxin GVIA (omega-CgTx), omega-conotoxin MVIIC (omega-MVIIC) and omega-conotoxin MVIID (omega-MVIID) were evaluated on transmitter release in the mouse diaphragm preparation. The effects of omega-AgaIVA and omega-MVIIC were also evaluated on the perineurial calcium and calcium-dependent potassium currents, ICa and IK(Ca), respectively, in the mouse levator auris preparation. 2. The P- and Q-type VDCC blocker omega-AgaIVA (100 nM) and P- Q- and N-type channel blockers omega-MVIIC (1 microM) and omega-MVIID (3 microM) strongly reduced transmitter release (> 80-90% blockade) whereas the selective N-type channel blocker omega-CgTx (5 microM) was ineffective. 3. The process of release was much more sensitive to omega-MVIIC (IC50 = 39 nM) than to omega-MVIID (IC50 = 1.4 microM). After almost completely blocking transmitter release (quantal content approximately 0.3% of its control value) with 3 microM omega-MVIIC, elevating the external [Ca2+] from 2 to 10 mM induced an increase of approximately 20 fold on the quantal content of the endplate potential (e.p.p.) (from 0.2 +/- 0.04 to 4.8 +/- 1.4). 4. Nerve-evoked transmitter release in a low Ca(2+)-high Mg2+ medium (low release probability, quantal content = 2 +/- 0.1) had the same sensitivity to omega-AgaIVA (IC50 = 16.8 nM) as that in normal saline solutions. In addition, K(+)-evoked transmitter release was also highly sensitive to the action of this toxin (IC50 = 11.5 nM; 100 nM > 95% blockade). The action of omega-AgaIVA on transmitter release could be reversed by toxin washout if the experiments were carried out at 31-33 degrees C. Conversely, the effect of omega-AgaIVA persisted even after two hours of toxin washout at room temperature. 5. Both the calcium and calcium-dependent potassium presynaptic currents, ICa and IK(Ca), respectively, were highly sensitive to low concentrations (10-30 nM) of omega-AgaIVA. The ICa and the IK(Ca) were also strongly reduced by 1 microM omega-MVIIC. The most marked difference between the action of these two toxins was the long incubation times required to achieve maximal effects with omega-MVIIC. 6. In summary these results provide more evidence that synaptic transmission at the mammalian neuromuscular junction is mediated by Ca2+ entry through P- and/or Q-type calcium channels.

The voltage-dependent calcium channels present in mammalian and chicken brain synaptosomes were characterized pharmacologically using specific blockers of L-type channels (1,4-dihydropyridines), N-type channels (omega-conotoxin GVIA), and P-type channels [funnel web toxin (FTX) and omega-agatoxin IVA]. K(+)-induced Ca2+ uptake by chicken synaptosomes was blocked by omega-conotoxin GVIA (IC50 = 250 nM). This toxin at 5 microM did not block Ca2+ entry into rat frontal cortex synaptosomes. FTX and omega-agatoxin IVA blocked Ca2+ uptake by rat synaptosomes (IC50 = 0.17 microliter/ml and 40 nM, respectively). Likewise, in chicken synaptosomes, FTX and omega-agatoxin IVA affected Ca2+ uptake, FTX (3 microliters/ml) exerted a maximal inhibition of 40% with an IC50 similar to the one obtained in rat preparations, whereas with omega-agatoxin IVA saturation was not reached even at 5 microM. In chicken preparations, the combined effect of saturating concentrations of FTX (1 microliter/ml) and different concentrations of omega-conotoxin GVIA showed no additive effects. However, the effect of saturating concentrations of FTX and omega-conotoxin GVIA was never greater than the one observed with omega-conotoxin GVIA. We also found that 60% of the Ca2+ uptake by rat and chicken synaptosomes was inhibited by omega-conotoxin MVIID (1 microM), a toxin that has a high index of discrimination against N-type channels. Conversely, nitrendipine (10 microM) had no significant effect on Ca2+ uptake in either the rat or the chicken. In conclusion, Ca2+ uptake by rat synaptosomes is potently inhibited by different P-type Ca2+ channel blockers, thus indicating that P-type channels are predominant in this preparation.(ABSTRACT TRUNCATED AT 250 WORDS)