Glutamatergic Nonpyramidal Neurons From Neocortical Layer VI and Their Comparison With Pyramidal and Spiny Stellate Neurons

The deeper part of neocortical layer VI is dominated by nonpyramidal neurons, which lack a prominent vertically ascending dendrite and predominantly establish corticocortical connections. These neurons were studied in rat neocortical slices using patch-clamp, single-cell reverse transcription–polymerase chain reaction, and biocytin labeling. The majority of these neurons expressed the vesicular glutamate transporter but not glutamic acid decarboxylase, suggesting that a high proportion of layer VI nonpyramidal neurons are glutamatergic. Indeed, they exhibited numerous dendritic spines and established asymmetrical synapses. Our sample of glutamatergic nonpyramidal neurons displayed a wide variety of somatodendritic morphologies and a subset of these cells expressed the Nurr1 mRNA, a marker for ipsilateral, but not commissural corticocortical projection neurons in layer VI. Comparison with spiny stellate and pyramidal neurons from other layers showed that glutamatergic neurons consistently exhibited a low occurrence of GABAergic interneuron markers and regular spiking firing patterns. Analysis of electrophysiological diversity using unsupervised clustering disclosed three groups of cells. Layer V pyramidal neurons were segregated into a first group, whereas a second group consisted of a subpopulation of layer VI neurons exhibiting tonic firing. A third heterogeneous cluster comprised spiny stellate, layer II/III pyramidal, and layer VI neurons exhibiting adaptive firing. The segregation of layer VI neurons in two different clusters did not correlate either with their somatodendritic morphologies or with Nurr1 expression. Our results suggest that electrophysiological similarities between neocortical glutamatergic neurons extend beyond layer positioning, somatodendritic morphology, and projection specificity.

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Heterogeneity of Phasic Cholinergic Signaling in Neocortical Neurons

Journal of Neurophysiology ◽

10.1152/jn.00493.2006 ◽

2007 ◽

Vol 97 (3) ◽

pp. 2215-2229 ◽

Cited By ~ 118

Author(s):

Allan T. Gulledge ◽

Susanna B. Park ◽

Yasuo Kawaguchi ◽

Greg J. Stuart

Keyword(s):

Visual Cortex ◽

Calcium Release ◽

Pyramidal Neurons ◽

Potassium Conductance ◽

Projection Neurons ◽

Sk Channels ◽

Cortical Areas ◽

Neocortical Neurons ◽

Cholinergic Signaling ◽

Nonpyramidal Neurons

Acetylcholine (ACh) is a neurotransmitter critical for normal cognition. Here we demonstrate heterogeneity of cholinergic signaling in neocortical neurons in the rat prefrontal, somatosensory, and visual cortex. Focal ACh application (100 μM) inhibited layer 5 pyramidal neurons in all cortical areas via activation of an apamin-sensitive SK-type calcium-activated potassium conductance. Cholinergic inhibition was most robust in prefrontal layer 5 neurons, where it relies on the same signal transduction mechanism (M1-like receptors, IP3-dependent calcium release, and SK-channels) as exists in somatosensory pyramidal neurons. Pyramidal neurons in layer 2/3 were less responsive to ACh, but substantial apamin-sensitive inhibitory responses occurred in deep layer 3 neurons of the visual cortex. ACh was only inhibitory when presented near the somata of layer 5 pyramidal neurons, where repetitive ACh applications generated discrete inhibitory events at frequencies of up to ∼0.5 Hz. Fast-spiking (FS) nonpyramidal neurons in all cortical areas were unresponsive to ACh. When applied to non-FS interneurons in layers 2/3 and 5, ACh generated mecamylamine-sensitive nicotinic responses (38% of cells), apamin-insensitive hyperpolarizing responses, with or without initial nicotinic depolarization (7% of neurons), or no response at all (55% of cells). Responses in interneurons were similar across cortical layers and regions but were correlated with cellular physiology and the expression of biochemical markers associated with different classes of nonpyramidal neurons. Finally, ACh generated nicotinic responses in all layer 1 neurons tested. These data demonstrate that phasic cholinergic input can directly inhibit projection neurons throughout the cortex while sculpting intracortical processing, especially in superficial layers.

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GABAergic neurons in the olfactory cortex projecting to the lateral hypothalamus in mice

10.1101/413328 ◽

2018 ◽

Author(s):

Koshi Murata ◽

Tomoki Kinoshita ◽

Yugo Fukazawa ◽

Kenta Kobayashi ◽

Kazuto Kobayashi ◽

...

Keyword(s):

Olfactory Bulb ◽

Lateral Hypothalamus ◽

Ventral Striatum ◽

Glutamate Transporter ◽

Olfactory Cortex ◽

Acid Decarboxylase ◽

Projection Neurons ◽

Diagonal Band ◽

Glutamate Transporter 1 ◽

Glutamic Acid Decarboxylase 65

AbstractOlfaction guides goal-directed behaviours including feeding. To investigate how central olfactory neural circuits control feeding behaviour in mice, we performed retrograde tracing from the lateral hypothalamus (LH), an important feeding centre. We observed a cluster of retrogradely labelled cells distributed in the posteroventral region of the olfactory peduncle. Histochemical analyses revealed that a majority of these retrogradely labelled projection neurons expressed glutamic acid decarboxylase 65/67 (GAD65/67), but not vesicular glutamate transporter 1 (VGluT1). We named this region with GABAergic projection neurons the ventral olfactory nucleus (VON) to discriminate it from the conventional olfactory peduncle. VON neurons were less immunoreactive for DARPP-32, a striatal neuron marker, in comparison to those in the olfactory tubercle and nucleus accumbens, which distinguished the VON from the ventral striatum. Fluorescent labelling confirmed synaptic contacts between VON neurons and olfactory bulb projection neurons. Rabies-virus-mediated trans-synaptic labelling revealed that VON neurons received synaptic inputs from the olfactory bulb, other olfactory cortices, horizontal limb of the diagonal band, and prefrontal cortex. Collectively, these results identified novel GABAergic projection neurons in the olfactory cortex that can integrate olfactory sensory and top-down inputs and send inhibitory output to the LH, which may contribute to forming odour-guided LH-related behaviours.

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Delineating the Organization of Projection Neuron Subsets with Multi-fluorescent Rabies Virus Tracing Tool

10.1101/2019.12.16.877258 ◽

2019 ◽

Author(s):

Liang Li ◽

Yajie Tang ◽

Leqiang Sun ◽

Jinsong Yu ◽

Hui Gong ◽

...

Keyword(s):

Rabies Virus ◽

Functional Organization ◽

Projection Neuron ◽

Projection Neurons ◽

Thalamic Nuclei ◽

Corticothalamic Projection ◽

Virus Tracing ◽

Layer V ◽

The Brain ◽

Layer Vi

AbstractThe elegant functions of the brain are facilitated by sophisticated connections between neurons, the architecture of which is frequently characterized by one nucleus connecting to multiple targets via projection neurons. Delineating the sub-nucleus fine architecture of projection neurons in a certain nucleus could greatly facilitate its circuit, computational, and functional resolution. Here, we developed multi-fluorescent rabies virus to delineate the fine organization of corticothalamic projection neuron subsets in the primary visual cortex (V1). By simultaneously labeling multiple distinct subsets of corticothalamic projection neurons in V1 from their target nuclei in thalamus (dLGN, LP, LD), we observed that V1-dLGN corticothalamic neurons were densely concentrated in layer VI, except for several sparsely scattered neurons in layer V, while V1-LP and V1-LD corticothalamic neurons were localized to both layers V and VI. Meanwhile, we observed a fraction of V1 corticothalamic neurons targeting multiple thalamic nuclei, which was further confirmed by fMOST whole-brain imaging. We further conceptually proposed an upgraded sub-nucleus tracing system with higher throughput (21 subsets) for more complex architectural tracing. The multi-fluorescent RV tracing tool can be extensively applied to resolve architecture of projection neuron subsets, with a strong potential to delineate the computational and functional organization of these nuclei.

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Anatomy, Physiology, and Synaptic Responses of Rat Layer V Auditory Cortical Cells and Effects of Intracellular GABAABlockade

Journal of Neurophysiology ◽

10.1152/jn.2000.83.5.2626 ◽

2000 ◽

Vol 83 (5) ◽

pp. 2626-2638 ◽

Cited By ~ 69

Author(s):

Brenda J. Hefti ◽

Philip H. Smith

Keyword(s):

Pyramidal Neurons ◽

Excitatory Input ◽

Projection Neurons ◽

Inhibitory Input ◽

Excitatory Postsynaptic Potential ◽

Channel Blockers ◽

Apparent Difference ◽

Cortical Cells ◽

Layer V ◽

Synaptic Responses

The varied extracortical targets of layer V make it an important site for cortical processing and output, which may be regulated by differences in the pyramidal neurons found there. Two populations of projection neurons, regular spiking (RS) and intrinsic bursting (IB), have been identified in layer V of some sensory cortices, and differences in their inhibitory inputs have been indirectly demonstrated. In this report, IB and RS cells were identified in rat auditory cortical slices, and differences in thalamocortical inhibition reaching RS and IB cells were demonstrated directly using intracellular GABAA blockers. Thalamocortical synaptic input to RS cells was always a combination of excitation and both GABAA and GABAB inhibition. Stimulation seldom triggered a suprathreshold response. IB cell synaptic responses were mostly excitatory, and stimulation usually triggered action potentials. This apparent difference was confirmed directly using intracellular chloride channel blockers. Before intracellular diffusion, synaptic responses were stable and similar to control conditions. Subsequently, GABAA was blocked, revealing a cell's total excitatory input. On GABAAblockade, RS cells responded to synaptic stimulation with large, suprathreshold excitatory events, indicating that excitation, while always present in these cells, is masked by GABAA. In IB cells that had visible GABAA input, it often masked an excitatory postsynaptic potential (EPSP) that could lead to additional suprathreshold events. These findings indicate that IB cells receive less GABAA-mediated inhibitory input and are able to spike or burst in response to thalamocortical synaptic stimulation far more readily than RS cells. Such differences may have implications for the influence each cell type exerts on its postsynaptic targets.

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Neurog2 and Ascl1 together regulate a postmitotic derepression circuit to govern laminar fate specification in the murine neocortex

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1701495114 ◽

2017 ◽

Vol 114 (25) ◽

pp. E4934-E4943 ◽

Cited By ~ 11

Author(s):

Daniel J. Dennis ◽

Grey Wilkinson ◽

Saiqun Li ◽

Rajiv Dixit ◽

Lata Adnani ◽

...

Keyword(s):

Cell Fate ◽

Deep Layer ◽

Projection Neurons ◽

Cell Fate Specification ◽

Transcriptional Repressors ◽

Gain Of Function ◽

Proneural Genes ◽

Fate Specification ◽

Layer V ◽

Layer Vi

A derepression mode of cell-fate specification involving the transcriptional repressors Tbr1, Fezf2, Satb2, and Ctip2 operates in neocortical projection neurons to specify six layer identities in sequence. Less well understood is how laminar fate transitions are regulated in cortical progenitors. The proneural genes Neurog2 and Ascl1 cooperate in progenitors to control the temporal switch from neurogenesis to gliogenesis. Here we asked whether these proneural genes also regulate laminar fate transitions. Several defects were observed in the derepression circuit in Neurog2−/−;Ascl1−/− mutants: an inability to repress expression of Tbr1 (a deep layer VI marker) during upper-layer neurogenesis, a loss of Fezf2+/Ctip2+ layer V neurons, and precocious differentiation of normally late-born, Satb2+ layer II–IV neurons. Conversely, in stable gain-of-function transgenics, Neurog2 promoted differentiative divisions and extended the period of Tbr1+/Ctip2+ deep-layer neurogenesis while reducing Satb2+ upper-layer neurogenesis. Similarly, acute misexpression of Neurog2 in early cortical progenitors promoted Tbr1 expression, whereas both Neurog2 and Ascl1 induced Ctip2. However, Neurog2 was unable to influence the derepression circuit when misexpressed in late cortical progenitors, and Ascl1 repressed only Satb2. Nevertheless, neurons derived from late misexpression of Neurog2 and, to a lesser extent, Ascl1, extended aberrant subcortical axon projections characteristic of early-born neurons. Finally, Neurog2 and Ascl1 altered the expression of Ikaros and Foxg1, known temporal regulators. Proneural genes thus act in a context-dependent fashion as early determinants, promoting deep-layer neurogenesis in early cortical progenitors via input into the derepression circuit while also influencing other temporal regulators.

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Nociceptive Processing by Anterior Cingulate Pyramidal Neurons

Journal of Neurophysiology ◽

10.1152/jn.00024.2010 ◽

2010 ◽

Vol 103 (6) ◽

pp. 3287-3301 ◽

Cited By ~ 24

Author(s):

Bai-Chuang Shyu ◽

Robert W. Sikes ◽

Leslie J. Vogt ◽

Brent A. Vogt

Keyword(s):

Pyramidal Neurons ◽

Cingulate Cortex ◽

Anterior Cingulate ◽

Projection Neurons ◽

Noxious Stimulation ◽

Axon Collateral ◽

Postsynaptic Potentials ◽

Nociceptive Responses ◽

Nociceptive Afferents ◽

Layer V

Although the cingulate cortex is frequently activated in acute human pain studies, postsynaptic responses are not known nor are links between nociceptive afferents, neuronal responses, and outputs to other structures. Intracellular potentials were recorded from neurobiotin-injected, pyramidal neurons in anterior cingulate area 24b following noxious stimulation of the sciatic nerve in anesthetized rabbits. Layer IIIc pyramids had extensive and horizontally oriented basal dendrites in layer IIIc where nociceptive afferents terminate. They had the longest excitatory postsynaptic potentials (EPSPs; 545 ms) that were modulated with hyperpolarizing currents. Pyramids in layer V had an intermediate tuft of oblique apical dendrites in layer IIIc that were 150–350 μm from somata in layer Va and 351–550 μm in layer Vb. Although average EPSP durations were short in layers II–IIIab (222 ± 31), Va (267 ± 65), and Vb (159 ± 31), there were five neurons in layers IIIab–Va that had EPSP durations lasting >300 ms (548 ± 63 ms). Neurons in layers IIIc, Va, and Vb had the highest amplitude EPSPs (6.25, 6.84 ± 0.58, and 6.4 ± 0.47 mV, respectively), whereas those in layers II–IIIab were 5 ± 0.56 mV. Nociceptive responses in layer Vb were complex and some had initial inhibitory postsynaptic potentials with shorter-duration EPSPs. Layers II–IIIab had dye-coupled pyramids and EPSPs in these layers had short durations (167 ± 33 ms) compared with those in layers IIIc–Va (487 ± 28 ms). In conclusion there are two populations of anterior cingulate cortex pyramids with EPSPs of significantly different durations, although their dendritic morphologies do not predict EPSP duration. Short-duration EPSPs are thalamic-mediated, nociceptive responses lasting ≤200 ms. Longer, “integrative” EPSPs are >350 ms and are likely modulated by intracortical axon collateral discharges. These findings suggest that links between nociception and projections to cortical and motor systems are instantaneous because nociceptive responses are generated directly by pyramidal projection neurons in all layers.

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Nicotinic activity depresses synaptic potentiation in layer V pyramidal neurons of mouse insular cortex

Neuroscience ◽

10.1016/j.neuroscience.2017.06.031 ◽

2017 ◽

Vol 358 ◽

pp. 13-27 ◽

Cited By ~ 13

Author(s):

Hajime Sato ◽

Tsutomu Kawano ◽

Dong Xu Yin ◽

Takafumi Kato ◽

Hiroki Toyoda

Keyword(s):

Pyramidal Neurons ◽

Insular Cortex ◽

Synaptic Potentiation ◽

Layer V

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β1- and β2-Adrenergic activations enhance excitatory synaptic transmission in layer V/VI pyramidal neurons of the medial prefrontal cortex of rats

Neuroscience Research ◽

10.1016/j.neures.2010.07.1989 ◽

2010 ◽

Vol 68 ◽

pp. e449

Author(s):

Zejun Feng

Keyword(s):

Prefrontal Cortex ◽

Synaptic Transmission ◽

Medial Prefrontal Cortex ◽

Pyramidal Neurons ◽

Excitatory Synaptic Transmission ◽

Layer V

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Septohippocampal transmission from parvalbumin-positive neurons features rapid recovery from synaptic depression

Scientific Reports ◽

10.1038/s41598-020-80245-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Feng Yi ◽

Tavita Garrett ◽

Karl Deisseroth ◽

Heikki Haario ◽

Emily Stone ◽

...

Keyword(s):

Pyramidal Neurons ◽

Synaptic Depression ◽

Medial Septum ◽

Membrane Properties ◽

Projection Neurons ◽

Calcium Dependent ◽

Light Pulses ◽

Diagonal Band ◽

Initial Release ◽

Intrinsic Membrane Properties

AbstractParvalbumin-containing projection neurons of the medial-septum-diagonal band of Broca ($$\hbox {PV}_{\text{MS-DBB}}$$ PV MS-DBB ) are essential for hippocampal rhythms and learning operations yet are poorly understood at cellular and synaptic levels. We combined electrophysiological, optogenetic, and modeling approaches to investigate $$\hbox {PV}_{\text{MS-DBB}}$$ PV MS-DBB neuronal properties. $$\hbox {PV}_{\text{MS-DBB}}$$ PV MS-DBB neurons had intrinsic membrane properties distinct from acetylcholine- and somatostatin-containing MS-DBB subtypes. Viral expression of the fast-kinetic channelrhodopsin ChETA-YFP elicited action potentials to brief (1–2 ms) 470 nm light pulses. To investigate $$\hbox {PV}_{\text{MS-DBB}}$$ PV MS-DBB transmission, light pulses at 5–50 Hz frequencies generated trains of inhibitory postsynaptic currents (IPSCs) in CA1 stratum oriens interneurons. Using a similar approach, optogenetic activation of local hippocampal PV ($$\hbox {PV}_{\text{HC}}$$ PV HC ) neurons generated trains of $$\hbox {PV}_{\text{HC}}$$ PV HC -mediated IPSCs in CA1 pyramidal neurons. Both synapse types exhibited short-term depression (STD) of IPSCs. However, relative to $$\hbox {PV}_{\text{HC}}$$ PV HC synapses, $$\hbox {PV}_{\text{MS-DBB}}$$ PV MS-DBB synapses possessed lower initial release probability, transiently resisted STD at gamma (20–50 Hz) frequencies, and recovered more rapidly from synaptic depression. Experimentally-constrained mathematical synapse models explored mechanistic differences. Relative to the $$\hbox {PV}_{\text{HC}}$$ PV HC model, the $$\hbox {PV}_{\text{MS-DBB}}$$ PV MS-DBB model exhibited higher sensitivity to calcium accumulation, permitting a faster rate of calcium-dependent recovery from STD. In conclusion, resistance of $$\hbox {PV}_{\text{MS-DBB}}$$ PV MS-DBB synapses to STD during short gamma bursts enables robust long-range GABAergic transmission from MS-DBB to hippocampus.

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