Showing papers by "Ole Paulsen published in 2013"
TL;DR: HbNES cells are the first demonstration of highly expandable neuroepithelial stem cells derived from the human embryo without genetic immortalization and provide a benchmark for the production of similar long-term neuroepIThelial-like stem cells (lt-NES) from pluripotent cell lines.
Abstract: Stem cell lines that faithfully maintain the regional identity and developmental potency of progenitors in the human brain would create new opportunities in developmental neurobiology and provide a resource for generating specialized human neurons. However, to date, neural progenitor cultures derived from the human brain have either been short-lived or exhibit restricted, predominantly glial, differentiation capacity. Pluripotent stem cells are an alternative source, but to ascertain definitively the identity and fidelity of cell types generated solely in vitro is problematic. Here, we show that hindbrain neuroepithelial stem (hbNES) cells can be derived and massively expanded from early human embryos (week 5-7, Carnegie stage 15-17). These cell lines are propagated in adherent culture in the presence of EGF and FGF2 and retain progenitor characteristics, including SOX1 expression, formation of rosette-like structures, and high neurogenic capacity. They generate GABAergic, glutamatergic and, at lower frequency, serotonergic neurons. Importantly, hbNES cells stably maintain hindbrain specification and generate upper rhombic lip derivatives on exposure to bone morphogenetic protein (BMP). When grafted into neonatal rat brain, they show potential for integration into cerebellar development and produce cerebellar granule-like cells, albeit at low frequency. hbNES cells offer a new system to study human cerebellar specification and development and to model diseases of the hindbrain. They also provide a benchmark for the production of similar long-term neuroepithelial-like stem cells (lt-NES) from pluripotent cell lines. To our knowledge, hbNES cells are the first demonstration of highly expandable neuroepithelial stem cells derived from the human embryo without genetic immortalization.
76 citations
TL;DR: Using sensory-evoked activity patterns recorded from the developing mouse cortex in vivo, the synaptic learning rule that is uncovered here relies solely on the presynaptic neuron and complements timing-based rules and is likely to play a role in the pruning of synaptic input during cortical development.
56 citations
TL;DR: GABAB receptors containing the GABAB1a subunit contribute to spontaneous termination ofUP states and are essential for afferent‐evoked termination of UP states.
Abstract: During slow-wave sleep, cortical neurons display synchronous fluctuations between periods of persistent activity ('UP states') and periods of relative quiescence ('DOWN states'). Such UP and DOWN states are also seen in isolated cortical slices. Recently, we reported that both spontaneous and evoked termination of UP states in slices from the rat medial entorhinal cortex (mEC) involves GABA(B) receptors. Here, in order to dissociate the roles of GABA(B1a)- and GABA(B1b)-containing receptors in terminating UP states, we used mEC slices from mice in which either the GABA(B1a) or the GABA(B1b) subunit had been genetically ablated. Pharmacological blockade of GABA(B) receptors using the antagonist CGP55845 prolonged the UP state duration in both wild-type mice and those lacking the GABA(B1b) subunit, but not in those lacking the GABA(B1a) subunit. Conversely, electrical stimulation of layer 1 could terminate an ongoing UP state in both wild-type mice and those lacking the GABA(B1a) subunit, but not in those lacking the GABA(B1b) subunit. Together with previous reports, indicating a preferential presynaptic location of GABA(B1a)- and postsynaptic location of GABA(B1b)-containing receptors, these results suggest that presynaptic GABA(B) receptors contribute to spontaneous DOWN state transitions, whilst postsynaptic GABA(B) receptors are essential for the afferent termination of the UP state. Inputs to layer 1 from other brain regions could thus provide a powerful mechanism for synchronizing DOWN state transitions across cortical areas via activation of GABAergic interneurons targeting postsynaptic GABA(B) receptors.
55 citations
TL;DR: D dopamine strongly and reversibly suppressed cortical UP states and it was shown that this effect was mediated through D1‐like and not D2‐like dopamine receptors, and there was no evidence that tonic dopaminergic transmission affected UP states in the authors' model.
Abstract: Cortical networks display persistent activity in the form of periods of sustained synchronous depolarizations (‘UP states’) punctuated by periods of relative hyperpolarization (‘DOWN states’), which together form the slow oscillation. UP states are known to be synaptically generated and are sustained by a dynamic balance of excitation and inhibition, with fast ionotropic glutamatergic excitatory and GABAergic inhibitory conductances increasing during the UP state. Previously, work from our group demonstrated that slow metabotropic GABA receptors also play an important role in terminating the UP state, but the effects of other neuromodulators on this network phenomenon have received little attention. Given that persistent activity is a neural correlate of working memory and that signalling through dopamine receptors has been shown to be critical for working memory tasks, we examined whether dopaminergic neurotransmission affected the slow oscillation. Here, using an in vitro model of the slow oscillation in rat medial entorhinal cortex, we showed that dopamine strongly and reversibly suppressed cortical UP states. We showed that this effect was mediated through D1-like and not D2-like dopamine receptors, and we found no evidence that tonic dopaminergic transmission affected UP states in our model.
24 citations
TL;DR: It is found that both CA3 and CA1 pyramidal neurons show a voltage sag in response to negative current steps but that this voltage sag is significantly smaller in CA3 cells, which is consistent with differential expression of Ih by the two cell types.
Abstract: The phase of firing of hippocampal neurons during theta oscillations encodes spatial information. Moreover, the spike phase response to synaptic inputs in individual cells depends on the expression of the hyperpolarisation-activated mixed cation current (Ih), which differs between CA3 and CA1 pyramidal neurons. Here, we compared the phase response of these two cell types, as well as their intrinsic membrane properties. We found that both CA3 and CA1 pyramidal neurons show a voltage sag in response to negative current steps but that this voltage sag is significantly smaller in CA3 cells. Moreover, CA3 pyramidal neurons have less prominent resonance properties compared to CA1 pyramidal neurons. This is consistent with differential expression of Ih by the two cell types. Despite their distinct intrinsic membrane properties, both CA3 and CA1 pyramidal neurons displayed bidirectional spike phase control by excitatory conductance inputs during theta oscillations. In particular, excitatory inputs delivered at the descending phase of a dynamic clamp-induced membrane potential oscillation delayed the subsequent spike by nearly 50 mrad. The effect was shown to be mediated by Ih and was counteracted by increasing inhibitory conductance driving the membrane potential oscillation. Using our experimental data to feed a computational model, we showed that differences in Ih between CA3 and CA1 pyramidal neurons could predict frequency-dependent differences in phase response properties between these cell types. We confirmed experimentally such frequency-dependent spike phase control in CA3 neurons. Therefore, a decrease in theta frequency, which is observed in intact animals during novelty, might switch the CA3 spike phase response from unidirectional to bidirectional and thereby promote encoding of the new context.
12 citations