scholarly journals Inhibitory Interactions Between Spiny Projection Neurons in the Rat Striatum

2002 ◽  
Vol 88 (3) ◽  
pp. 1263-1269 ◽  
Author(s):  
Mark J. Tunstall ◽  
Dorothy E. Oorschot ◽  
Annabel Kean ◽  
Jeffery R. Wickens
Keyword(s):  
Action Potential ◽  
Brain Slices ◽  
Reversal Potential ◽  
Rat Striatum ◽  
Projection Neurons ◽  
Single Action ◽  
Presynaptic Action ◽  
Synaptic Interactions ◽  
Striatal Projection Neurons ◽  
Inhibitory Interactions

The spiny projection neurons are by far the most numerous type of striatal neuron. In addition to being the principal projection neurons of the striatum, the spiny projection neurons also have an extensive network of local axon collaterals by which they make synaptic connections with other striatal projection neurons. However, up to now there has been no direct physiological evidence for functional inhibitory interactions between spiny projection neurons. Here we present new evidence that striatal projection neurons are interconnected by functional inhibitory synapses. To examine the physiological properties of unitary inhibitory postsynaptic potentials (IPSPs), dual intracellular recordings were made from pairs of spiny projection neurons in brain slices of adult rat striatum. Synaptic interactions were found in 9 of 45 pairs of neurons using averages of 200 traces that were triggered by a single presynaptic action potential. In all cases, synaptic interactions were unidirectional, and no bidirectional interactions were detected. Unitary IPSPs evoked by a single presynaptic action potential had a peak amplitude ranging from 157 to 319 μV in different connections (mean: 277 ± 46 μV, n = 9). The percentage of failures of single action potentials to evoke a unitary IPSP was estimated and ranged from 9 to 63% (mean: 38 ± 14%, n = 9). Unitary IPSPs were reversibly blocked by bicuculline ( n = 4) and had a reversal potential of −62.4 ± 0.7 mV ( n = 5), consistent with GABA-mediated inhibition. The findings of the present study correlate very well with anatomical evidence for local synaptic connectivity between spiny projection neurons and suggest that lateral inhibition plays a significant role in the information processing operations of the striatum.

scholarly journals Morphological Characterization of the Action Potential Initiation Segment in GnRH Neuron Dendrites and Axons of Male Mice

Endocrinology ◽  
2015 ◽  
Vol 156 (11) ◽  
pp. 4174-4186 ◽  
Author(s):  
Michel K. Herde ◽  
Allan E. Herbison
Keyword(s):  
Action Potential ◽  
Cell Body ◽  
Brain Slices ◽  
Gnrh Neuron ◽  
Male Mice ◽  
Single Action ◽  
Ankyrin G ◽  
Gnrh Neurons ◽  
Action Potential Initiation ◽  
Potential Initiation

GnRH neurons are the final output neurons of the hypothalamic network controlling fertility in mammals. In the present study, we used ankyrin G immunohistochemistry and neurobiotin filling of live GnRH neurons in brain slices from GnRH-green fluorescent protein transgenic male mice to examine in detail the location of action potential initiation in GnRH neurons with somata residing at different locations in the basal forebrain. We found that the vast majority of GnRH neurons are bipolar in morphology, elaborating a thick (primary) and thinner (secondary) dendrite from opposite poles of the soma. In addition, an axon-like process arising predominantly from a proximal dendrite was observed in a subpopulation of GnRH neurons. Ankyrin G immunohistochemistry revealed the presence of a single action potential initiation zone ∼27 μm in length primarily in the secondary dendrite of GnRH neurons and located 30 to 140 μm distant from the cell soma, depending on the type of process and location of the cell body. In addition to dendrites, the GnRH neurons with cell bodies located close to hypothalamic circumventricular organs often elaborated ankyrin G–positive axon-like structures. Almost all GnRH neurons (>90%) had their action potential initiation site in a process that initially, or ultimately after a hairpin loop, was coursing in the direction of the median eminence. These studies indicate that action potentials are initiated in different dendritic and axonal compartments of the GnRH neuron in a manner that is dependent partly on the neuroanatomical location of the cell body.

scholarly journals Cell Assembly Dynamics of Sparsely-connected Inhibitory Networks: a Simple Model for the Collective Activity of Striatal Projection Neurons

2016 ◽  
Author(s):  
David Angulo-Garcia ◽  
Joshua D. Berke ◽  
Alessandro Torcini
Keyword(s):  
Brain Slices ◽  
Temporal Organization ◽  
Projection Neurons ◽  
Cell Assembly ◽  
Population Activity ◽  
Specific Sequence ◽  
Cell Assemblies ◽  
Inhibitory Network ◽  
Striatal Projection Neurons ◽  
Inhibitory Networks

Striatal projection neurons form a sparsely-connected inhibitory network, and this arrangement may be essential for the appropriate temporal organization of behavior. Here we show that a simplified, sparse inhibitory network of Leaky-Integrate-and-Fire neurons can reproduce some key features of striatal population activity, as observed in brain slices. In particular we develop a new metric to determine the conditions under which sparse inhibitory networks form anti-correlated cell assemblies with time-varying activity of individual cells. We find that under these conditions the network displays an input-specific sequence of cell assembly switching, that effectively discriminates similar inputs. Our results support the proposal that GABAergic connections between striatal projection neurons allow stimulus-selective, temporally-extended sequential activation of cell assemblies. Furthermore, we help to show how altered intrastriatal GABAergic signaling may produce aberrant network-level information processing in disorders such as Parkinson's and Huntington's diseases.

Ionic basis of presynaptic inhibitory potentials at crayfish claw opener

1980 ◽  
Vol 43 (6) ◽  
pp. 1547-1557 ◽  
Author(s):  
P. A. Fuchs ◽  
P. A. Getting
Keyword(s):  
Action Potential ◽  
Procambarus Clarkii ◽  
Chloride Concentration ◽  
Reversal Potential ◽  
Synaptic Potential ◽  
Single Action ◽  
Rest Potential ◽  
External Potassium ◽  
A Charge ◽  
Ionic Basis

1. Intracellular recordings from the claw opener excitor axon of the crayfish, Procambarus clarkii, were obtained near the terminal arborizations of the axon on the surface of the opener muscle. Rest potential in the excitor axon averaged --80 mV over 20 cells. Action-potential amplitude and duration averaged 100 mV and 2 ms, respectively. 2. A single action potential in the opener inhibitor axon produces a hyperpolarizing synaptic potential (average amplitude 0.3 mV) in the excitor axon. The apparent reversal potential of this inhibitory synaptic potential is approximately 5 mV more negative than rest in control saline. No excitor axons were observed to have depolarizing synaptic potentials at rest. 3. A decrease in external chloride concentration from 240 to 24 mM causes the apparent reversal potential to depolarize an average of 12 mV, with no change in rest potential. In low-chloride saline, the synaptic potential evoked by stimulation of the inhibitor axon becomes depolarizing. 4. An increase in external potassium concentration from 5 to 10 mM causes the apparent reversal potential to depolarize by 16 mV; however, rest potential depolarizes by 10 mV. Low external potassium has the opposite effects, causing both rest potential and the apparent reversal potential to hyperpolarize. 5. Presynaptic inhibition at the Procambarus claw opener neuromuscular junction appears to be mediated by a hyperpolarizing synaptic potential. The results of these experiments suggest that chloride serves as the charge for the presynaptic potential. The evidence for a direct involvement of potassium as a charge carrier is equivocal due to Donnan equilibrium effects involving Cl.

Evidence for Persistent Na+ Current in Apical Dendrites of Rat Neocortical Neurons From Imaging of Na+-Sensitive Dye

1997 ◽  
Vol 78 (2) ◽  
pp. 1188-1192 ◽  
Author(s):  
Thomas Mittmann ◽  
Shannon M. Linton ◽  
Peter Schwindt ◽  
Wayne Crill
Keyword(s):  
Action Potential ◽  
Brain Slices ◽  
Apical Dendrite ◽  
Fluorescence Signal ◽  
Camera System ◽  
Single Action ◽  
Single Action Potential ◽  
Neocortical Neurons ◽  
Fluorescence Change ◽  
Apical Dendrites

Mittmann, Thomas, Shannon M. Linton, Peter Schwindt, and Wayne Crill. Evidence for persistent Na+ current in apical dendrites of rat neocortical neurons from imaging of Na+-sensitive dye. J. Neurophysiol. 78: 1188–1192, 1997. Evidence for a persistent Na+ current ( I NaP) in the apical dendrite of neocortical neurons was sought with the use of fluorescence imaging to measure changes in intradendritic Na+ concentration. Neurons in neocortical brain slices were filled iontophoretically through an intracellular recording microelectrode with the Na+-sensitive dye benzofuran isophthalate (SBFI), and fluorescence images were recorded with a cooled charge-coupled device camera system using 380-nm illumination. In the presence of Ca2+ and K+ channel blockers, a short depolarizing current pulse evoked a single action potential followed by a plateau depolarization (PD) lasting >1 s. This tetrodotoxin (TTX)-sensitive PD is known to be maintained by I NaP. A single action potential caused no detectable SBFI fluorescence change, whereas the PD was associated with an SBFI fluorescence change in the soma and apical dendrite indicating increased intracellular Na+ concentration. Determination of the full spatial extent of the dendritic fluorescence change was prevented by our inability to detect the dim fluorescence signal in the distal regions of the apical dendrite. In each experiment the fluorescence change extended into the apical dendrite as far as dye could be visualized (50–300 μm). A slow, depolarizing voltage-clamp ramp that activated I NaP caused similar fluorescence changes that were eliminated by TTX, indicating that the SBFI fluorescence changes are caused by Na+ influx due to I NaP activation. We conclude that I NaP can be generated by the apical dendritic membrane to at least 300 μm from the soma.

scholarly journals Excitatory GABAergic Effects in Striatal Projection Neurons

2006 ◽  
Vol 95 (2) ◽  
pp. 1285-1290 ◽  
Author(s):  
Enrico Bracci ◽  
Stefano Panzeri
Keyword(s):  
Action Potentials ◽  
Brain Slices ◽  
Current Injection ◽  
Projection Neurons ◽  
Current Clamp ◽  
Spike Threshold ◽  
Striatal Projection Neurons ◽  
Glutamate Receptor Antagonists ◽  
Apparent Reduction ◽  
Whole Cell Recordings

The ability of synaptically released GABA to facilitate action potential generation in striatal projection neurons was studied in brain slices using current-clamp, gramicidin-perforated whole cell recordings. Evoked GABAergic postsynaptic potentials (PSPs) were pharmacologically isolated with ionotropic glutamate receptor antagonists. Subthreshold depolarizing current injections were paired with GABAergic PSPs at different intervals. GABAergic PSPs were able to convert current injection-induced depolarizations from subthreshold to suprathreshold, but only when they preceded the current injection by an appropriate interval; accordingly, action potentials were observed 4–140 ms after the onset of the GABAergic PSP, and their likelihood was maximal after 50–60 ms. The GABAergic excitatory effects were fully blocked by the GABAA receptor antagonist bicuculline. Appropriately timed GABA PSPs decreased the time taken by current injections to depolarize projection neurons, causing an apparent reduction in the spike threshold. In control solution, the ability of evoked PSPs (comprising both glutamatergic and GABAergic components) to reach spike threshold was often impaired by bicuculline. We conclude that GABAergic PSPs can exert excitatory effects on projection neurons and that this ability crucially depends on the timing between the GABAergic event and a concomitant depolarizing input.

Contribution of the low-threshold T-type calcium current in generating the post-spike depolarizing afterpotential in dentate granule neurons of immature rats

1993 ◽  
Vol 70 (1) ◽  
pp. 223-231 ◽  
Author(s):  
L. Zhang ◽  
T. A. Valiante ◽  
P. L. Carlen
Keyword(s):  
Action Potential ◽  
Strong Dependence ◽  
Brain Slices ◽  
Membrane Resistance ◽  
Membrane Hyperpolarization ◽  
Single Action ◽  
Bath Application ◽  
Immature Rats ◽  
Ionic Mechanisms ◽  
Inward Currents

1. The underlying ionic mechanisms of the postspike depolarizing afterpotential (DAP) in hippocampal dentate granule (DG) neurons of immature rats (postnatal 7- to 17-day-old) were examined using whole cell patch recordings in brain slices. 2. In current-clamp mode, the DAP followed each single action potential. Graded DAP-like responses were also evoked by depolarizing current pulses when the action potential was blocked by tetrodotoxin (TTX), demonstrating that the TTX-sensitive Na+ conductance is not necessary for DAP generation. The membrane resistance near the DAP peak was lower than at rest, suggesting activation of inward currents rather than blockade of outward currents during the DAP. The DAP peak amplitude showed a strong dependence on voltage, increasing with membrane hyperpolarization and decreasing with depolarization in the range of -90 to -50 mV. Repetitive stimulation at 1-2 Hz did not change the amplitude or decay of the DAP or DAP-like response. 3. Bath application of 2 mM 4-aminopyridine (4-AP) and 5 mM tetraethylammonium chloride (TEA) prolonged the action potential and enhanced the DAP, suggesting that the DAP waveform is determined by the interaction of voltage-activated outward K+ currents and inward currents. 4. Bath application of 2 mM Co2+ depressed the DAP and the DAP-like potential. Replacement of extracellular Ca2+ with Ba2+ potentiated the DAP. Intracellular Ca2+ chelation with the fast chelator, bis-(o-aminophenoxy)-N,N,N',N'-tetraacetic acid (BAPTA), only slightly enhanced the DAP, suggesting that the DAP is not generated by inward currents activated secondary to Ca2+ influx.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Dynamics and Compartmentalization in Leech Neurons

2005 ◽  
Vol 94 (6) ◽  
pp. 4430-4440 ◽  
Author(s):  
Sofija Andjelic ◽  
Vincent Torre
Keyword(s):  
Information Processing ◽  
Action Potential ◽  
Action Potentials ◽  
Time Course ◽  
Ccd Camera ◽  
Calcium Dynamics ◽  
Single Action ◽  
Single Action Potential ◽  
Calcium Indicator ◽  
Mechanosensory Neurons

Calcium dynamics in leech neurons were studied using a fast CCD camera. Fluorescence changes (Δ F/ F) of the membrane impermeable calcium indicator Oregon Green were measured. The dye was pressure injected into the soma of neurons under investigation. Δ F/ F caused by a single action potential (AP) in mechanosensory neurons had approximately the same amplitude and time course in the soma and in distal processes. By contrast, in other neurons such as the Anterior Pagoda neuron, the Annulus Erector motoneuron, the L motoneuron, and other motoneurons, APs evoked by passing depolarizing current in the soma produced much larger fluorescence changes in distal processes than in the soma. When APs were evoked by stimulating one distal axon through the root, Δ F/ F was large in all distal processes but very small in the soma. Our results show a clear compartmentalization of calcium dynamics in most leech neurons in which the soma does not give propagating action potentials. In such cells, the soma, while not excitable, can affect information processing by modulating the sites of origin and conduction of AP propagation in distal excitable processes.

scholarly journals Inhibition of Phosphodiesterase 10A Increases the Responsiveness of Striatal Projection Neurons to Cortical Stimulation

2008 ◽  
Vol 328 (3) ◽  
pp. 785-795 ◽  
Author(s):  
Sarah Threlfell ◽  
Stephen Sammut ◽  
Frank S. Menniti ◽  
Christopher J. Schmidt ◽  
Anthony R. West
Keyword(s):  
Cortical Stimulation ◽  
Projection Neurons ◽  
Striatal Projection Neurons ◽  
Phosphodiesterase 10A
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