A method for labeling embryonic rat medial septal region projection neurons, in vitro, using fluorescent tracers

Projection neurons of the substantia nigra reticulata (SNr) convey basal ganglia (BG) processing to thalamocortical and brain stem circuits responsible for movement. Two models try to explain pathological BG performance during Parkinson disease (PD): the rate model, which posits an overexcitation of SNr neurons due to hyperactivity in the indirect pathway and hypoactivity of the direct pathway, and the oscillatory model, which explains PD as the product of pathological pattern generators disclosed by dopamine reduction. These models are, apparently, incompatible. We tested the predictions of the rate model by increasing the excitatory drive and reducing the inhibition on SNr neurons in vitro. This was done pharmacologically with bath application of glutamate agonist N-methyl-d-aspartate and GABAA receptor blockers, respectively. Both maneuvers induced bursting behavior in SNr neurons. Therefore synaptic changes forecasted by the rate model induce the electrical behavior predicted by the oscillatory model. In addition, we found evidence that CaV3.2 Ca2+ channels are a critical step in generating the bursting firing pattern in SNr neurons. Other ion channels involved are: hyperpolarization-activated cation channels, high-voltage-activated Ca2+ channels, and Ca2+-activated K+ channels. However, although these channels shape the temporal structure of bursting, only CaV3.2 Ca2+ channels are indispensable for the initiation of the bursting pattern.

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Vertebrate retinal ganglion cells are selected from competent progenitors by the action of Notch

Development ◽

10.1242/dev.121.11.3637 ◽

1995 ◽

Vol 121 (11) ◽

pp. 3637-3650 ◽

Cited By ~ 33

Author(s):

C.P. Austin ◽

D.E. Feldman ◽

J.A. Ida ◽

C.L. Cepko

Keyword(s):

Cell Fate ◽

Ganglion Cells ◽

Notch Pathway ◽

Cell Types ◽

Projection Neurons ◽

Specific Cell ◽

Vitro Assay ◽

Notch Activity

The first cells generated during development of the vertebrate retina are the ganglion cells, the projection neurons of the retina. Although they are one of the most intensively studied cell types within the central nervous system, little is known of the mechanisms that determine ganglion cell fate. We demonstrate that ganglion cells are selected from a large group of competent progenitors that comprise the majority of the early embryonic retina and that differentiation within this group is regulated by Notch. Notch activity in vivo was diminished using antisense oligonucleotides or augmented using a retrovirally transduced constitutively active allele of Notch. The number of ganglion cells produced was inversely related to the level of Notch activity. In addition, the Notch ligand Delta inhibited retinal progenitors from differentiating as ganglion cells to the same degree as did activated Notch in an in vitro assay. These results suggest a conserved strategy for neurogenesis in the retina and describe a versatile in vitro and in vivo system with which to examine the action of the Notch pathway in a specific cell fate decision in a vertebrate.

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Dopamine Excites Fast-Spiking Interneurons in the Striatum

Journal of Neurophysiology ◽

10.1152/jn.00754.2001 ◽

2002 ◽

Vol 87 (4) ◽

pp. 2190-2194 ◽

Cited By ~ 99

Author(s):

Enrico Bracci ◽

Diego Centonze ◽

Giorgio Bernardi ◽

Paolo Calabresi

Keyword(s):

Input Resistance ◽

Projection Neurons ◽

Dopamine Receptor Agonist ◽

Gabaergic Interneurons ◽

Synaptic Currents ◽

Cholinergic Interneurons ◽

Endogenous Dopamine ◽

Excitatory Action ◽

Fast Spiking

The striatum is the main recipient of dopaminergic innervation. Striatal projection neurons are controlled by cholinergic and GABAergic interneurons. The effects of dopamine on projection neurons and cholinergic interneurons have been described. Its action on GABAergic interneurons, however, is still unknown. We studied the effects of dopamine on fast-spiking (FS) GABAergic interneurons in vitro, with intracellular recordings. Bath application of dopamine elicited a depolarization accompanied by an increase in membrane input resistance (an effect that persisted in the presence of tetrodotoxin) and action-potential discharge. These effects were mimicked by the D1-like dopamine receptor agonist SKF38393 but not by the D2-like agonist quinpirole. Evoked corticostriatal glutamatergic synaptic currents were not affected by dopamine. Conversely, GABAergic currents evoked by intrastriatal stimulation were reversibly depressed by dopamine and D2-like, but not D1-like, agonists. Cocaine elicited effects similar to those of dopamine on membrane potential and synaptic currents. These results show that endogenous dopamine exerts a dual excitatory action on FS interneurons, by directly depolarizing them (through D1-like receptors) and by reducing their synaptic inhibition (through presynaptic D2-like receptors).

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Differential electroresponsiveness of stellate and pyramidal-like cells of medial entorhinal cortex layer II

Journal of Neurophysiology ◽

10.1152/jn.1993.70.1.128 ◽

1993 ◽

Vol 70 (1) ◽

pp. 128-143 ◽

Cited By ~ 279

Author(s):

A. Alonso ◽

R. Klink

Keyword(s):

Membrane Potential ◽

Entorhinal Cortex ◽

Morphological Characteristics ◽

Oscillatory Activity ◽

Inward Rectification ◽

Projection Neurons ◽

Medial Entorhinal Cortex ◽

Mean Frequency ◽

Subthreshold Oscillations

1. The electroresponsive properties of neurons from layer II of the rat medial entorhinal cortex (MEC) were studied by intracellular recording under current clamp in an in vitro brain slice preparation. From a total of 184 cells that fulfilled our criteria for recording stability, two groups of projection neurons were distinguished on the basis of their intrinsic biophysical properties and morphological characteristics (demonstrated by intracellular biocytin injection; n = 34). 2. Stellate cells (SCs) were the most abundant (69%). They were highly electroresponsive, and minimal changes (1-3 mV) of membrane potential generated an active response. Subthreshold depolarizing or hyperpolarizing current pulse injection always caused the membrane potential to attain an early peak and then sag to a lower level. Depolarization-induced "sags" were larger and determined early firing in all cells. The voltage-current relationship of SCs was markedly non-linear, demonstrating robust inward rectification in the hyperpolarizing and depolarizing range. 3. SCs generated persistent rhythmic subthreshold voltage oscillations on DC depolarization positive to -60 mV. The mean frequency of the oscillations was 8.6 Hz (theta range) at a membrane potential of approximately -55 mV, at which level occasional single spiking also occurred. At slightly more positive potentials, a striking 1- to 3-Hz repetitive bursting pattern emerged. This consisted of nonadapting trains of spikes ("clusters") interspersed with subthreshold oscillations that had a mean frequency of 21.7 Hz (beta range). 4. Nonstellate cells (39%; mostly pyramidal-like) displayed time-dependent inward rectification that was less pronounced than that of SCs, and minimal depolarization-induced sags. On threshold depolarization, firing was always preceded by a slowly rising ramp depolarization and thus occurred with a long delay. Inward rectification in the depolarizing range was very pronounced. However, non-SCs did not generate persistent rhythmic subthreshold oscillatory activity or spike clusters. 5. Of the electrophysiological parameters quantified, spike threshold, spike duration, depolarizing afterpotential amplitude and apparent membrane time constant demonstrated statistically significant differences between SCs and non-SCs. 6. The repetitive hiring properties in response to square current pulses of short duration (< 500 ms) were also different between SCs and non-SCs. First, most SCs displayed a bilinear frequency-current (f-I) relationship for only the first interspike interval, whereas most non-SCs displayed a bilinear relationship for all intervals. Second, SCs had a much steeper primary f-I slope for early intervals than non-SCs. Finally, SCs displayed more pronounced and faster spike frequency adaptation than non-SCs.(ABSTRACT TRUNCATED AT 400 WORDS)

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Dopamine Modulates Excitability of Basolateral Amygdala Neurons In Vitro

Journal of Neurophysiology ◽

10.1152/jn.00843.2004 ◽

2005 ◽

Vol 93 (3) ◽

pp. 1598-1610 ◽

Cited By ~ 104

Author(s):

Sven Kröner ◽

J. Amiel Rosenkranz ◽

Anthony A. Grace ◽

German Barrionuevo

Keyword(s):

Basolateral Amygdala ◽

Neuronal Response ◽

Brain Slices ◽

Receptor Activation ◽

D1 Receptor ◽

In Vivo Studies ◽

Projection Neurons ◽

Direct Effects

The amygdala plays a role in affective behaviors, which are modulated by the dopamine (DA) innervation of the basolateral amygdala complex (BLA). Although in vivo studies indicate that activation of DA receptors alters BLA neuronal activity, it is unclear whether DA exerts direct effects on BLA neurons or whether it acts via indirect effects on BLA afferents. Using whole cell patch-clamp recordings in rat brain slices, we investigated the site and mechanisms through which DA regulates the excitability of BLA neurons. Dopamine enhanced the excitability of BLA projection neurons in response to somatic current injections via a postsynaptic effect. Dopamine D1 receptor activation increased excitability and evoked firing, whereas D2 receptor activation increased input resistance. Current- and voltage-clamp experiments in projection neurons showed that D1 receptor activation enhanced excitability by modulating a 4-aminopyridine- and α-dendrotoxin-sensitive, slowly inactivating K+ current. Furthermore, DA and D1 receptor activation increased evoked firing in fast-spiking BLA interneurons. Consistent with a postsynaptic modulation of interneuron excitability, DA also increased the frequency of spontaneous inhibitory postsynaptic currents recorded in projection neurons without changing release of GABA. These data demonstrate that DA exerts direct effects on BLA projection neurons and indirect actions via modulation of interneurons that may work in concert to enhance the neuronal response to large, suprathreshold inputs, while suppressing weaker inputs.

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Mass Generation, Neuron Labeling, and 3D Imaging of Minibrains

Frontiers in Bioengineering and Biotechnology ◽

10.3389/fbioe.2020.582650 ◽

2021 ◽

Vol 8 ◽

Author(s):

Subashika Govindan ◽

Laura Batti ◽

Samira F. Osterop ◽

Luc Stoppini ◽

Adrien Roux

Keyword(s):

Large Scale ◽

3D Imaging ◽

Cell Types ◽

Mixed Population ◽

Projection Neurons ◽

Neuron Morphology ◽

Mass Generation ◽

One Step ◽

Human Ipsc

Minibrain is a 3D brain in vitro spheroid model, composed of a mixed population of neurons and glial cells, generated from human iPSC derived neural stem cells. Despite the advances in human 3D in vitro models such as aggregates, spheroids and organoids, there is a lack of labeling and imaging methodologies to characterize these models. In this study, we present a step-by-step methodology to generate human minibrain nurseries and novel strategies to subsequently label projection neurons, perform immunohistochemistry and 3D imaging of the minibrains at large multiplexable scales. To visualize projection neurons, we adapt viral transduction and to visualize the organization of cell types we implement immunohistochemistry. To facilitate 3D imaging of minibrains, we present here pipelines and accessories for one step mounting and clearing suitable for confocal microscopy. The pipelines are specifically designed in such a way that the assays can be multiplexed with ease for large-scale screenings using minibrains and other organoid models. Using the pipeline, we present (i) dendrite morphometric properties obtained from 3D neuron morphology reconstructions, (ii) diversity in neuron morphology, and (iii) quantified distribution of progenitors and POU3F2 positive neurons in human minibrains.

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Fezf2 transient expression via modRNA with concurrent SIRT1 inhibition enhances differentiation of cortical subcerebral / corticospinal neuron identity from mES cells

10.1101/2020.08.13.242230 ◽

2020 ◽

Author(s):

Cameron Sadegh ◽

Wataru Ebina ◽

Anthony C. Arvanites ◽

Lance S. Davidow ◽

Lee L. Rubin ◽

...

Keyword(s):

Stem Cell ◽

Cortical Neurons ◽

Embryonic Stem ◽

Induced Pluripotent Stem Cell ◽

Sirtuin 1 ◽

Projection Neurons ◽

Specific Expression ◽

Specific Differentiation

AbstractDuring late embryonic development of the cerebral cortex, the major class of cortical output neurons termed subcerebral projection neurons (SCPN; including the predominant population of corticospinal neurons, CSN) and the class of interhemispheric callosal projection neurons (CPN) initially express overlapping molecular controls that later undergo subtype-specific refinements. Such molecular refinements are largely absent in heterogeneous, maturation-stalled, neocortical-like neurons (termed “cortical” here) spontaneously generated by established embryonic stem cell (ES) and induced pluripotent stem cell (iPSC) differentiation. Building on recently identified central molecular controls over SCPN development, we used a combination of synthetic modified mRNA (modRNA) for Fezf2, the central transcription factor controlling SCPN specification, and small molecule screening to investigate whether distinct chromatin modifiers might complement Fezf2 functions to promote SCPN-specific differentiation by mouse ES (mES)-derived cortical-like neurons. We find that the inhibition of a specific histone deacetylase, Sirtuin 1 (SIRT1), enhances refinement of SCPN subtype molecular identity by both mES-derived cortical-like neurons and primary dissociated E12.5 mouse cortical neurons. In vivo, we identify that SIRT1 is specifically expressed by CPN, but not SCPN, during late embryonic and postnatal differentiation. Together, these data indicate that SIRT1 has neuronal subtype-specific expression in the mouse cortex in vivo, and its inhibition enhances subtype-specific differentiation of highly clinically relevant SCPN / CSN cortical neurons in vitro.

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Differential chromatin accessibility in developing projection neurons is correlated with transcriptional regulation of cell fate

10.1101/645572 ◽

2019 ◽

Author(s):

Whitney E. Heavner ◽

Shaoyi Ji ◽

James H. Notwell ◽

Ethan S. Dyer ◽

Alex M. Tseng ◽

...

Keyword(s):

Gene Expression ◽

Progenitor Cells ◽

Cell Fate ◽

Expression Profiles ◽

Chromatin Accessibility ◽

Transcriptional Networks ◽

Projection Neurons ◽

Cortical Projection ◽

Functional Features

AbstractWe are only just beginning to catalog the vast diversity of cell types in the cerebral cortex. Such categorization is a first step toward understanding how diversification relates to function. All cortical projection neurons arise from a uniform pool of progenitor cells that lines the ventricles of the forebrain. It is still unclear how these progenitor cells generate the more than fifty unique types of mature cortical projection neurons defined by their distinct gene expression profiles. Here we compare gene expression and chromatin accessibility of two subclasses of projection neurons with divergent morphological and functional features as they develop in the mouse brain between embryonic day 13 and postnatal day 5 in order to identify transcriptional networks that diversity neuron cell fate. We find groups of transcription factors whose expression is correlated with chromatin accessibility, transcription factor binding motifs, and lncRNAs that define each subclass and validate the function of a family of novel candidate genes in vitro. Our multidimensional approach reveals that subclass-specific chromatin accessibility is significantly correlated with gene expression, providing a resource for generating new specific genetic drivers and revealing regions of the genome that are particularly susceptible to harmful genetic mutations by virtue of their correlation with important developmental genes.

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Aberrant development of hippocampal circuits and altered neural activity in netrin 1-deficient mice

Development ◽

10.1242/dev.127.22.4797 ◽

2000 ◽

Vol 127 (22) ◽

pp. 4797-4810 ◽

Cited By ~ 1

Author(s):

M.J. Barallobre ◽

J.A. Del Rio ◽

S. Alcantara ◽

V. Borrell ◽

F. Aguado ◽

...

Keyword(s):

Neural Activity ◽

Surface Proteins ◽

Projection Neurons ◽

Commissural Axons ◽

Fiber Tracts ◽

Spontaneous Neural Activity ◽

Spontaneous Neuronal Activity ◽

Deficient Mice

Diffusible factors, including netrins and semaphorins, are believed to be important cues for the formation of neural circuits in the forebrain. Here we have examined the role of netrin 1 in the development of hippocampal connections. We show that netrin 1 and its receptor, Dcc, are expressed in the developing fimbria and in projection neurons, respectively, and that netrin 1 promotes the outgrowth of hippocampal axons in vitro via DCC receptors. We also show that the hippocampus of netrin 1-deficient mice shows a misorientation of fiber tracts and pathfinding errors, as detected with antibodies against the surface proteins TAG-1, L1 and DCC. DiI injections show that hippocampal commissural axons do not cross the midline in these mutants. Instead, when axons approach the midline, they turn ventrally and form a massive aberrant projection to the ipsilateral septum. In addition, both the ipsilateral entorhino-hippocampal and the CA3-to-CA1 associational projections show an altered pattern of layer-specific termination in netrin 1-deficient mice. Finally, optical recordings with the Ca(2+) indicator Fura 2-AM show that spontaneous neuronal activity is reduced in the septum of netrin 1-mutant mice. We conclude that netrin 1 is required not only for the formation of crossed connections in the forebrain, but also for the appropriate layer-specific targeting of ipsilateral projections and for the control of normal levels of spontaneous neural activity.

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