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A new measure for the strength of electrical synapses.

Haas JS - Front Cell Neurosci (2015)

Bottom Line: Electrical synapses are typically quantified by subthreshold measurements of coupling, which fall short in describing their impact on spiking activity in coupled neighbors.This method, also applicable to neurotransmitter-based synapses, communicates the considerable strength of electrical synapses.For electrical synapses measured in rodent slices of the thalamic reticular nucleus and in simple model neurons, spike timing is modulated by tens of ms by activity in a coupled neighbor.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Lehigh University Bethlehem, PA, USA.

ABSTRACT
Electrical synapses, like chemical synapses, mediate intraneuronal communication. Electrical synapses are typically quantified by subthreshold measurements of coupling, which fall short in describing their impact on spiking activity in coupled neighbors. Here, we describe a novel measurement for electrical synapse strength that directly evaluates the effect of synaptically transmitted activity on spike timing. This method, also applicable to neurotransmitter-based synapses, communicates the considerable strength of electrical synapses. For electrical synapses measured in rodent slices of the thalamic reticular nucleus and in simple model neurons, spike timing is modulated by tens of ms by activity in a coupled neighbor.

No MeSH data available.


Related in: MedlinePlus

(A) Coupling demonstrated by a hyperpolarizing current pulse in a pair of simple Hodgkin-Huxley neurons; cc = 0.15. Scale bar 2 mV, 25 ms. (B) Spiking one of the model cells (blue) for a minimal input (lower, gray); the coupled neuron was quiet. (C) Spiking in the same cell (light blue) for the same current pulses as in (A) (lower, shown in gray), with the coupled neighbor also spiking (lower, shown in green). Responses from (A) are repeated, vertically offset, for clarity (dark blue). Scale bar 10 mV, 25 ms. (D) δL plotted against coupling coefficient in the modeled pair, for three values of excitability [sodium conductances of 60 (pink), 75 (maroon) and 90 (red) μS/cm2].
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Figure 4: (A) Coupling demonstrated by a hyperpolarizing current pulse in a pair of simple Hodgkin-Huxley neurons; cc = 0.15. Scale bar 2 mV, 25 ms. (B) Spiking one of the model cells (blue) for a minimal input (lower, gray); the coupled neuron was quiet. (C) Spiking in the same cell (light blue) for the same current pulses as in (A) (lower, shown in gray), with the coupled neighbor also spiking (lower, shown in green). Responses from (A) are repeated, vertically offset, for clarity (dark blue). Scale bar 10 mV, 25 ms. (D) δL plotted against coupling coefficient in the modeled pair, for three values of excitability [sodium conductances of 60 (pink), 75 (maroon) and 90 (red) μS/cm2].

Mentions: Because spiking in TRN neurons is heavily influenced by their low-threshold T current, we repeated measurement of δL in a coupled pair of simple Hodgkin-Huxley neurons (Figure 4). We used model neurons identical to those used in Sevetson and Haas (2014), but with zero T conductance, reducing the model to only sodium and potassium currents with a linear and symmetrical electrical synapse. For minimal stimuli, we applied step inputs that yielded initial latencies of ~75 ms (Figure 4B). For a moderate value of coupling (cc = 0.15), activity across the electrical synapse accelerated the model neuron’s spike time from 70–55 ms, or δL of 21% (Figure 4C). To test the dependence of neuronal excitability on δL, we varied sodium conductance in the model by 25–50% (Figure 4D). Using minimal stimuli in each set showed that while δL is weakly related to excitability, the strong modulatory effect of electrical synapses on spike times is reproduced by this simple model.


A new measure for the strength of electrical synapses.

Haas JS - Front Cell Neurosci (2015)

(A) Coupling demonstrated by a hyperpolarizing current pulse in a pair of simple Hodgkin-Huxley neurons; cc = 0.15. Scale bar 2 mV, 25 ms. (B) Spiking one of the model cells (blue) for a minimal input (lower, gray); the coupled neuron was quiet. (C) Spiking in the same cell (light blue) for the same current pulses as in (A) (lower, shown in gray), with the coupled neighbor also spiking (lower, shown in green). Responses from (A) are repeated, vertically offset, for clarity (dark blue). Scale bar 10 mV, 25 ms. (D) δL plotted against coupling coefficient in the modeled pair, for three values of excitability [sodium conductances of 60 (pink), 75 (maroon) and 90 (red) μS/cm2].
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4585165&req=5

Figure 4: (A) Coupling demonstrated by a hyperpolarizing current pulse in a pair of simple Hodgkin-Huxley neurons; cc = 0.15. Scale bar 2 mV, 25 ms. (B) Spiking one of the model cells (blue) for a minimal input (lower, gray); the coupled neuron was quiet. (C) Spiking in the same cell (light blue) for the same current pulses as in (A) (lower, shown in gray), with the coupled neighbor also spiking (lower, shown in green). Responses from (A) are repeated, vertically offset, for clarity (dark blue). Scale bar 10 mV, 25 ms. (D) δL plotted against coupling coefficient in the modeled pair, for three values of excitability [sodium conductances of 60 (pink), 75 (maroon) and 90 (red) μS/cm2].
Mentions: Because spiking in TRN neurons is heavily influenced by their low-threshold T current, we repeated measurement of δL in a coupled pair of simple Hodgkin-Huxley neurons (Figure 4). We used model neurons identical to those used in Sevetson and Haas (2014), but with zero T conductance, reducing the model to only sodium and potassium currents with a linear and symmetrical electrical synapse. For minimal stimuli, we applied step inputs that yielded initial latencies of ~75 ms (Figure 4B). For a moderate value of coupling (cc = 0.15), activity across the electrical synapse accelerated the model neuron’s spike time from 70–55 ms, or δL of 21% (Figure 4C). To test the dependence of neuronal excitability on δL, we varied sodium conductance in the model by 25–50% (Figure 4D). Using minimal stimuli in each set showed that while δL is weakly related to excitability, the strong modulatory effect of electrical synapses on spike times is reproduced by this simple model.

Bottom Line: Electrical synapses are typically quantified by subthreshold measurements of coupling, which fall short in describing their impact on spiking activity in coupled neighbors.This method, also applicable to neurotransmitter-based synapses, communicates the considerable strength of electrical synapses.For electrical synapses measured in rodent slices of the thalamic reticular nucleus and in simple model neurons, spike timing is modulated by tens of ms by activity in a coupled neighbor.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Lehigh University Bethlehem, PA, USA.

ABSTRACT
Electrical synapses, like chemical synapses, mediate intraneuronal communication. Electrical synapses are typically quantified by subthreshold measurements of coupling, which fall short in describing their impact on spiking activity in coupled neighbors. Here, we describe a novel measurement for electrical synapse strength that directly evaluates the effect of synaptically transmitted activity on spike timing. This method, also applicable to neurotransmitter-based synapses, communicates the considerable strength of electrical synapses. For electrical synapses measured in rodent slices of the thalamic reticular nucleus and in simple model neurons, spike timing is modulated by tens of ms by activity in a coupled neighbor.

No MeSH data available.


Related in: MedlinePlus