Preferential cholinergic excitation of corticopontine neurons

AbstractPyramidal neurons in layer 5 of the neocortex comprise two broad classes of projection neurons: corticofugal neurons, including corticopontine (CPn) neurons, and intratelencephalic neurons, including commissural/callosal (COM) neurons. These non-overlapping neuron subpopulations represent discrete cortical output channels contributing to perception, decision making, and behavior. CPn and COM neurons have distinct morphological and physiological characteristics, and divergent responses to modulatory transmitters such as serotonin and acetylcholine (ACh). To better understand how ACh regulates cortical output, in slices of mouse prefrontal cortex (PFC) we compared the responsivity of CPn and COM neurons to transient exposure to exogenous or endogenous ACh. In both neuron subtypes, exogenous ACh generated qualitatively similar biphasic responses in which brief hyperpolarization was followed by longer-lasting enhancement of excitability. However, cholinergic inhibition was more pronounced in COM neurons, while excitatory responses were larger and longer lasting in CPn neurons. Similarly, optically triggered release of endogenous ACh from cholinergic terminals preferentially and persistently (for ~40 s) enhanced the excitability of CPn neurons, but had little impact on COM neurons. Cholinergic excitation of CPn neurons involved at least three distinct ionic mechanisms: activation of a calcium-sensitive but calcium-permeable nonspecific cation conductance, suppression of Kv7 channels (the “M-current”), and activation of the calcium-dependent nonspecific cation conductance underlying afterdepolarizations. Our results demonstrate projection-specific selectivity in cholinergic signaling in the PFC, and suggest that transient release of ACh during behavior will preferentially promote corticofugal output.

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Mechanisms underlying serotonergic excitation of callosal projection neurons

10.1101/197624 ◽

2017 ◽

Author(s):

Emily K. Stephens ◽

Arielle L. Baker ◽

Allan T. Gulledge

Keyword(s):

Intracellular Calcium ◽

Cortical Neurons ◽

Pyramidal Neurons ◽

Projection Neurons ◽

Calcium Dependent ◽

M Current ◽

Cation Conductance ◽

Cortical Pyramidal Neurons ◽

Excitatory Responses ◽

Callosal Projection

AbstractSerotonin (5-HT) selectively excites subpopulations of pyramidal neurons in the neocortex via activation of 5-HT2A (2A) receptors coupled to Gq subtype G-protein alpha subunits. Gq-mediated excitatory responses have been attributed primarily to suppression of potassium conductances, including those mediated by KV7 potassium channels (i.e., the M-current), or activation of nonspecific cation conductances that underly calcium-dependent afterdepolarizations (ADPs). However, 2A-dependent excitation of cortical neurons has not been extensively studied, and no consensus exists regarding the underlying ionic effector(s) involved. We tested potential mechanisms of serotonergic excitation in commissural/callosal projection neurons (COM neurons) in layer 5 of the mouse medial prefrontal cortex, a subpopulation of cortical pyramidal neurons that exhibit 2A-dependent excitation in response to 5-HT. In baseline conditions, 5-HT enhanced the rate of action potential generation in COM neurons experiencing suprathreshold somatic current injection. This serotonergic excitation was occluded by activation of muscarinic acetylcholine (ACh) receptors, confirming that 5-HT acts via the same Gq-signaling cascades engaged by ACh. Like ACh, 5-HT promoted the generation of calcium-dependent ADPs following spike trains. However, calcium was not necessary for serotonergic excitation, as responses to 5-HT were enhanced (by >100%), rather than reduced, by chelation of intracellular calcium with 10 mM BAPTA. This suggests intracellular calcium negatively regulates additional ionic conductances contributing to 2A excitation. Removal of extracellular calcium had no effect when intracellular calcium signaling was intact, but suppressed 5-HT response amplitudes, by about 50% (i.e., back to normal baseline values) when BAPTA was included in patch pipettes. This suggests that 2A excitation involves activation of a nonspecific cation conductance that is both calcium-sensitive and calcium-permeable. M-current suppression was found to be a third ionic effector, as blockade of KV7 channels with XE991 (10 μM) reduced serotonergic excitation by ∼50% in control conditions, and by ∼30% with intracellular BAPTA present. These findings demonstrate a role for at least three distinct ionic effectors, including KV7 channels, a calcium-sensitive and calcium-permeable nonspecific cation conductance, and the calcium-dependent ADP conductance, in mediating serotonergic excitation of COM neurons.

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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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Similar Inhibitory Processes Dominate the Responses of Cat Lateral Amygdaloid Projection Neurons to Their Various Afferents

Journal of Neurophysiology ◽

10.1152/jn.1997.77.1.341 ◽

1997 ◽

Vol 77 (1) ◽

pp. 341-352 ◽

Cited By ~ 73

Author(s):

E. J. Lang ◽

D. Paré

Keyword(s):

Companion Paper ◽

Rapid Onset ◽

Projection Neurons ◽

Excitatory Postsynaptic Potential ◽

Primary Role ◽

Inhibitory Processes ◽

Postsynaptic Potential ◽

Ionic Mechanisms ◽

Excitatory Responses ◽

The Impact

Lang, E. J. and D. Paré. Similar inhibitory processes dominate the responses of cat lateral amygdaloid projection neurons to their various afferents. J. Neurophysiol. 77: 341–352, 1997. To investigate the impact of inhibitory processes on responses of lateral amygdaloid (LAT) neurons, intracellular recordings were obtained from identified LAT projection neurons in barbiturate-anesthetized cats. Synaptic responses evoked by perirhinal (PRH), entorhinal (ENT), basomedial, and LAT stimulation were investigated. Regardless of stimulation site, responses consisted of an excitatory postsynaptic potential (EPSP) that either preceded and was truncated by an inhibitory postsynaptic potential (IPSP) or occurred just after the IPSP onset. IPSPs were monophasic, lasted hundreds of milliseconds, and were of such large amplitude and rapid onset that they effectively opposed the EPSPs, generally preventing orthodromic spikes. All sites elicited IPSPs with relatively negative reversal potentials around −85 mV. Experiments analyzing the underlying ionic mechanisms are presented in the companion paper. Evoked responses were similar to synaptic potentials associated with spontaneous EEG events, known as simple (small, monophasic) and complex (large, triphasic) ENT sharp potentials (SPs), with no difference between the reversals of evoked and SP-related IPSPs (−83.2 ± 2.7 mV). IPSPs coinciding with complex SPs truncated SP-related EPSPs more rapidly and had larger amplitudes and longer durations than those related to simple SPs. These differences reflected the fact that the amplitude and duration of SP-related IPSPs were correlated with SP amplitude. Similar variations were reproduced in evoked IPSPs by varying the stimulus intensity. Low intensities generated predominantly excitatory responses consisting of EPSPs sometimes followed by small IPSPs, whereas high intensities evoked predominantly inhibitory responses comprised of a large IPSP that truncated or occluded the EPSPs. Orthodromic spikes were elicited only in a narrow range of intermediate intensities. These changes in the evoked response primarily reflected increases in the IPSP evoked at high intensities. PRH stimulation at different rostro-caudal levels demonstrated that rostral sites elicited larger EPSPs and IPSPs with shorter latencies and longer durations than caudal sites. These differences probably reflect contrasting patterns of activity spread through the PRH cortex, suggesting that the intact cortical circuitry allowed a temporally distributed activation of inhibitory interneurons and thereby partly explains the long duration and monophasic nature of the IPSPs. Inhibition, thus, plays a primary role in shaping LAT neuronal responses. The profuse intrinsic connectivity of the LAT nucleus and parahippocampal cortices may underlie the relatively invariant response pattern of LAT neurons and suggests a common mode of information processing, based upon quantitative, rather than qualitative, differences in activation of LAT circuitry. Therefore we propose that effective transmission of signals through the LAT nucleus may require activation of specifically sized neuronal ensembles, rather than widespread afferent excitation.

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Serotonin has different effects on two classes of Betz cells from the cat

Journal of Neurophysiology ◽

10.1152/jn.1994.72.4.1925 ◽

1994 ◽

Vol 72 (4) ◽

pp. 1925-1937 ◽

Cited By ~ 26

Author(s):

W. J. Spain

Keyword(s):

Firing Rate ◽

Potassium Conductance ◽

Membrane Conductance ◽

Constant Current ◽

Repetitive Firing ◽

Calcium Dependent ◽

Constant Current Stimulation ◽

Ionic Mechanisms ◽

Betz Cells

1. Intracellular recording from cat Betz cells in vitro revealed a strong correlation between the dominant effect of serotonin (5-HT) and the Betz cell subtype in which it occurred. In large Betz cells that show posthyperpolarization excitation (termed PHE cells), 5-HT evoked a long-lasting membrane depolarization, whereas 5-HT evoked an initial hyperpolarization of variable duration in smaller Betz cells that show posthyperpolorization inhibition (termed PHI cells). 2. Voltage-clamp studies revealed that 5-HT caused a depolarizing shift of activation of the cation current Ih, which resulted in the depolarization in PHE cells, whereas the hyperpolarization in PHI cells is caused by an increase in a resting potassium conductance. 3. The effect of 5-HT on firing properties during constant current stimulation also differed consistently in the two types of Betz cells. In PHE cells the initial firing rate increased after 5-HT application, but the steady firing was unaffected. The depolarizing shift of Ih activation caused the increase of initial firing rate. 4. In PHI cells 5-HT caused a decrease in spike frequency adaptation. The decrease in adaptation was caused by a combination of two conductance changes. First, 5-HT caused a slow afterdepolarization in PHI cells that could trigger repetitive firing in the absence of further stimulation. The sADP depended on calcium entry through voltage-gated channels and was associated with a decrease in membrane conductance. Second, 5-HT caused reduction of a slow calcium-dependent potassium current that normally contributes to slow adaptation. 5. In conclusion, the effect of 5-HT on excitability differs systematically in Betz cell subtypes in part because they have different dominant ionic mechanisms that are modulated. If we assume that PHE cells and PHI cells represent fast and slow pyramidal tract (PT) neurons respectively, 5-HT will cause early recruitment of fast PT cells and delay recruitment of slow PT cells during low levels of synaptic excitation.

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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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A selective projection from the subthalamic nucleus to parvalbumin-expressing interneurons of the striatum

10.1101/2020.11.26.400242 ◽

2020 ◽

Author(s):

Krishnakanth Kondabolu ◽

Natalie M. Doig ◽

Olaoluwa Ayeko ◽

Bakhtawer Khan ◽

Alexandra Torres ◽

...

Keyword(s):

Basal Ganglia ◽

Subthalamic Nucleus ◽

Ex Vivo ◽

Cell Types ◽

Projection Neurons ◽

Striatal Neurons ◽

Primary Input ◽

Cholinergic Interneurons ◽

Axonal Connections ◽

Excitatory Responses

AbstractThe striatum and subthalamic nucleus (STN) are considered to be the primary input nuclei of the basal ganglia. Projection neurons of both striatum and STN can extensively interact with other basal ganglia nuclei, and there is growing anatomical evidence of direct axonal connections from the STN to striatum. There remains, however, a pressing need to elucidate the organization and impact of these subthalamostriatal projections in the context of the diverse cell types constituting the striatum. To address this, we carried out monosynaptic retrograde tracing from genetically-defined populations of dorsal striatal neurons in adult male and female mice, quantifying the connectivity from STN neurons to spiny projection neurons, GABAergic interneurons, and cholinergic interneurons. In parallel, we used a combination of ex vivo electrophysiology and optogenetics to characterize the responses of a complementary range of dorsal striatal neuron types to activation of STN axons. Our tracing studies showed that the connectivity from STN neurons to striatal parvalbumin-expressing interneurons is significantly higher (~ four-to eight-fold) than that from STN to any of the four other striatal cell types examined. In agreement, our recording experiments showed that parvalbumin-expressing interneurons, but not the other cell types tested, commonly exhibited robust monosynaptic excitatory responses to subthalamostriatal inputs. Taken together, our data collectively demonstrate that the subthalamostriatal projection is highly selective for target cell type. We conclude that glutamatergic STN neurons are positioned to directly and powerfully influence striatal activity dynamics by virtue of their enriched innervation of GABAergic parvalbumin-expressing interneurons.

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Features Of Hippocampal Astrocytic Domains And Their Spatial Relation To Excitatory And Inhibitory Neurons

10.1101/2020.05.25.114348 ◽

2020 ◽

Author(s):

Ron Refaeli ◽

Adi Doron ◽

Aviya Benmelech-Chovav ◽

Maya Groysman ◽

Tirzah Kreisel ◽

...

Keyword(s):

Spatial Distribution ◽

Pyramidal Neurons ◽

Spatial Relation ◽

Design Principles ◽

Inhibitory Neurons ◽

Computational Tools ◽

Close Proximity ◽

Somatostatin Neurons ◽

And Behavior ◽

Elaborate Structure

SUMMARYThe mounting evidence for the involvement of astrocytes in neuronal circuits function and behavior stands in stark contrast to the lack of detailed anatomical description of these cells and the neurons in their domains. To fill this void, we imaged >30,000 astrocytes in cleared hippocampi, and employed converging genetic, histological and computational tools to determine the elaborate structure, distribution and neuronal content of astrocytic domains. First, we characterized the spatial distribution of >19,000 astrocytes across CA1 lamina, and analyzed the detailed morphology of thousands of reconstructed domains. We then determined the excitatory content of CA1 astrocytes, averaging above 13 pyramidal neurons per domain and increasing towards CA1 midline. Finally, we discovered that somatostatin neurons are found in close proximity to astrocytes, compared to parvalbumin and VIP inhibitory neurons. This resource expands our understanding of fundamental hippocampal design principles, and provides the first quantitative foundation for neuron-astrocyte interactions in this region.

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Target-specific M1 inputs to infragranular S1 pyramidal neurons

Journal of Neurophysiology ◽

10.1152/jn.01032.2015 ◽

2016 ◽

Vol 116 (3) ◽

pp. 1261-1274 ◽

Cited By ~ 11

Author(s):

Amanda K. Kinnischtzke ◽

Erika E. Fanselow ◽

Daniel J. Simons

Keyword(s):

Primary Motor Cortex ◽

Pyramidal Neurons ◽

Projection Neurons ◽

Cell Type ◽

Intrinsic Properties ◽

Subcortical Structures ◽

Medial Nucleus ◽

Cell Type Specific ◽

Posterior Medial Nucleus

The functional role of input from the primary motor cortex (M1) to primary somatosensory cortex (S1) is unclear; one key to understanding this pathway may lie in elucidating the cell-type specific microcircuits that connect S1 and M1. Recently, we discovered that a subset of pyramidal neurons in the infragranular layers of S1 receive especially strong input from M1 (Kinnischtzke AK, Simons DJ, Fanselow EE. Cereb Cortex 24: 2237–2248, 2014), suggesting that M1 may affect specific classes of pyramidal neurons differently. Here, using combined optogenetic and retrograde labeling approaches in the mouse, we examined the strengths of M1 inputs to five classes of infragranular S1 neurons categorized by their projections to particular cortical and subcortical targets. We found that the magnitude of M1 synaptic input to S1 pyramidal neurons varies greatly depending on the projection target of the postsynaptic neuron. Of the populations examined, M1-projecting corticocortical neurons in L6 received the strongest M1 inputs, whereas ventral posterior medial nucleus-projecting corticothalamic neurons, also located in L6, received the weakest. Each population also possessed distinct intrinsic properties. The results suggest that M1 differentially engages specific classes of S1 projection neurons, thereby regulating the motor-related influence S1 exerts over subcortical structures.

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Developmental Regulation of Basket Interneuron Synapses and Behavior through NCAM in Mouse Prefrontal Cortex

Cerebral Cortex ◽

10.1093/cercor/bhaa074 ◽

2020 ◽

Vol 30 (8) ◽

pp. 4689-4707

Author(s):

Chelsea S Sullivan ◽

Vishwa Mohan ◽

Paul B Manis ◽

Sheryl S Moy ◽

Young Truong ◽

...

Keyword(s):

Prefrontal Cortex ◽

Pyramidal Neurons ◽

Developmental Regulation ◽

Brain Slices ◽

Pyramidal Cells ◽

Electrophysiological Recording ◽

Network Function ◽

Growth Cone Collapse ◽

Layer 2 ◽

And Behavior

Abstract Parvalbumin (PV)-expressing basket interneurons in the prefrontal cortex (PFC) regulate pyramidal cell firing, synchrony, and network oscillations. Yet, it is unclear how their perisomatic inputs to pyramidal neurons are integrated into neural circuitry and adjusted postnatally. Neural cell adhesion molecule NCAM is expressed in a variety of cells in the PFC and cooperates with EphrinA/EphAs to regulate inhibitory synapse density. Here, analysis of a novel parvalbumin (PV)-Cre: NCAM F/F mouse mutant revealed that NCAM functions presynaptically in PV+ basket interneurons to regulate postnatal elimination of perisomatic synapses. Mutant mice exhibited an increased density of PV+ perisomatic puncta in PFC layer 2/3, while live imaging in mutant brain slices revealed fewer puncta that were dynamically eliminated. Furthermore, EphrinA5-induced growth cone collapse in PV+ interneurons in culture depended on NCAM expression. Electrophysiological recording from layer 2/3 pyramidal cells in mutant PFC slices showed a slower rise time of inhibitory synaptic currents. PV-Cre: NCAM F/F mice exhibited impairments in working memory and social behavior that may be impacted by altered PFC circuitry. These findings suggest that the density of perisomatic synapses of PV+ basket interneurons is regulated postnatally by NCAM, likely through EphrinA-dependent elimination, which is important for appropriate PFC network function and behavior.

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Astrocyte dysfunction increases cortical dendritic excitability and promotes cranial pain in familial migraine

Science Advances ◽

10.1126/sciadv.aaz1584 ◽

2020 ◽

Vol 6 (23) ◽

pp. eaaz1584 ◽

Cited By ~ 3

Author(s):

Jennifer Romanos ◽

Dietmar Benke ◽

Daniela Pietrobon ◽

Hanns Ulrich Zeilhofer ◽

Mirko Santello

Keyword(s):

Mouse Model ◽

Pyramidal Neurons ◽

Glutamate Uptake ◽

Cingulate Cortex ◽

Familial Hemiplegic Migraine ◽

Strong Impact ◽

Two Photon Microscopy ◽

Genetic Mouse Model ◽

Cortical Physiology ◽

And Behavior

Astrocytes are essential contributors to neuronal function. As a consequence, disturbed astrocyte-neuron interactions are involved in the pathophysiology of several neurological disorders, with a strong impact on brain circuits and behavior. Here, we describe altered cortical physiology in a genetic mouse model of familial hemiplegic migraine type 2 (FHM2), with reduced expression of astrocytic Na+,K+-ATPases. We used whole-cell electrophysiology, two-photon microscopy, and astrocyte gene rescue to demonstrate that an impairment in astrocytic glutamate uptake promotes NMDA spike generation in dendrites of cingulate cortex pyramidal neurons and enhances output firing of these neurons. Astrocyte compensation of the defective ATPase in the cingulate cortex rescued glutamate uptake, prevented abnormal NMDA spikes, and reduced sensitivity to cranial pain triggers. Together, our results demonstrate that impaired astrocyte function alters neuronal activity in the cingulate cortex and facilitates migraine-like cranial pain states in a mouse model of migraine.

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