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The temporoammonic input to the hippocampal CA1 region displays distinctly different synaptic plasticity compared to the Schaffer collateral input in vivo: significance for synaptic information processing.

Aksoy-Aksel A, Manahan-Vaughan D - Front Synaptic Neurosci (2013)

Bottom Line: We observed that field excitatory postsynaptic potentials at the pp-CA1 synapse have longer onset latencies and a shorter time-to-peak compared to the Sc-CA1 synapse.LTP (>24 h) was successfully evoked by tetanic afferent stimulation of pp-CA1 synapses.Paired-pulse responses also showed significant differences.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurophysiology, Medical Faculty, Ruhr University Bochum Bochum, Germany ; International Graduate School for Neuroscience, Ruhr University Bochum Bochum, Germany.

ABSTRACT
In terms of its sub-regional differentiation, the hippocampal CA1 region receives cortical information directly via the perforant (temporoammonic) path (pp-CA1 synapse) and indirectly via the tri-synaptic pathway where the last relay station is the Schaffer collateral-CA1 synapse (Sc-CA1 synapse). Research to date on pp-CA1 synapses has been conducted predominantly in vitro and never in awake animals, but these studies hint that information processing at this synapse might be distinct to processing at the Sc-CA1 synapse. Here, we characterized synaptic properties and synaptic plasticity at the pp-CA1 synapse of freely behaving adult rats. We observed that field excitatory postsynaptic potentials at the pp-CA1 synapse have longer onset latencies and a shorter time-to-peak compared to the Sc-CA1 synapse. LTP (>24 h) was successfully evoked by tetanic afferent stimulation of pp-CA1 synapses. Low frequency stimulation evoked synaptic depression at Sc-CA1 synapses, but did not elicit LTD at pp-CA1 synapses unless the Schaffer collateral afferents to the CA1 region had been severed. Paired-pulse responses also showed significant differences. Our data suggest that synaptic plasticity at the pp-CA1 synapse is distinct from the Sc-CA1 synapse and that this may reflect its specific role in hippocampal information processing.

No MeSH data available.


Related in: MedlinePlus

Input/Output characteristics for the Sc-CA1, pp-CA1, and Sc-cut synapse. The fEPSP slope was recorded as the maximum slope from the beginning of the potential to the first minimum value for each subject. For each intensity of stimulation the values are expressed as percentage of the highest value obtained. There was no significant difference between Sc-CA1, SC-severed (Sc-cut) or pp-CA1 groups (n = 8 for Sc-CA1, n = 8 for Sc-cut and n = 9 for pp-CA1). Typical evoked responses from Sc-CA1, Sc-cut, and pp-CA1 animals embedded in the chart. Increasing the stimulation intensity stepwise (100–900 μA, step size 100 μA) complicated the analysis of the fEPSPs from the pp-CA1 and Sc-cut synapse to same extent. Vertical scale bar: 3 mV, horizontal scale bar: 5 ms.
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Figure 3: Input/Output characteristics for the Sc-CA1, pp-CA1, and Sc-cut synapse. The fEPSP slope was recorded as the maximum slope from the beginning of the potential to the first minimum value for each subject. For each intensity of stimulation the values are expressed as percentage of the highest value obtained. There was no significant difference between Sc-CA1, SC-severed (Sc-cut) or pp-CA1 groups (n = 8 for Sc-CA1, n = 8 for Sc-cut and n = 9 for pp-CA1). Typical evoked responses from Sc-CA1, Sc-cut, and pp-CA1 animals embedded in the chart. Increasing the stimulation intensity stepwise (100–900 μA, step size 100 μA) complicated the analysis of the fEPSPs from the pp-CA1 and Sc-cut synapse to same extent. Vertical scale bar: 3 mV, horizontal scale bar: 5 ms.

Mentions: Increasing the stimulation intensity in a stepwise manner did not affect the shape of the Sc-CA1 potentials drastically, but resulted in a steeper slope and increased amplitude. However, the same procedure increased the complexity of the pp-CA1 potentials by adding volume-conducted currents due to the stimulation of the DG, and a second negative-going potential, due to the subsequent activation of the CA3 region (Figure 3). Severance of the Sc fibers neither changed the general appearance nor the response to increase in stimulation for the pp synapse. For all groups the I/O curves had similar characteristics (Sc-CA1 compared to pp-CA1 or Sc-cut for all stimulation intensities p > 0.05; Figure 3). Consequently the stimulation intensity used for plasticity experiments corresponded to the range of 100–250 μA (intensity of stimulation to elicit 40% of the maximum fEPSP slope) for all groups.


The temporoammonic input to the hippocampal CA1 region displays distinctly different synaptic plasticity compared to the Schaffer collateral input in vivo: significance for synaptic information processing.

Aksoy-Aksel A, Manahan-Vaughan D - Front Synaptic Neurosci (2013)

Input/Output characteristics for the Sc-CA1, pp-CA1, and Sc-cut synapse. The fEPSP slope was recorded as the maximum slope from the beginning of the potential to the first minimum value for each subject. For each intensity of stimulation the values are expressed as percentage of the highest value obtained. There was no significant difference between Sc-CA1, SC-severed (Sc-cut) or pp-CA1 groups (n = 8 for Sc-CA1, n = 8 for Sc-cut and n = 9 for pp-CA1). Typical evoked responses from Sc-CA1, Sc-cut, and pp-CA1 animals embedded in the chart. Increasing the stimulation intensity stepwise (100–900 μA, step size 100 μA) complicated the analysis of the fEPSPs from the pp-CA1 and Sc-cut synapse to same extent. Vertical scale bar: 3 mV, horizontal scale bar: 5 ms.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750210&req=5

Figure 3: Input/Output characteristics for the Sc-CA1, pp-CA1, and Sc-cut synapse. The fEPSP slope was recorded as the maximum slope from the beginning of the potential to the first minimum value for each subject. For each intensity of stimulation the values are expressed as percentage of the highest value obtained. There was no significant difference between Sc-CA1, SC-severed (Sc-cut) or pp-CA1 groups (n = 8 for Sc-CA1, n = 8 for Sc-cut and n = 9 for pp-CA1). Typical evoked responses from Sc-CA1, Sc-cut, and pp-CA1 animals embedded in the chart. Increasing the stimulation intensity stepwise (100–900 μA, step size 100 μA) complicated the analysis of the fEPSPs from the pp-CA1 and Sc-cut synapse to same extent. Vertical scale bar: 3 mV, horizontal scale bar: 5 ms.
Mentions: Increasing the stimulation intensity in a stepwise manner did not affect the shape of the Sc-CA1 potentials drastically, but resulted in a steeper slope and increased amplitude. However, the same procedure increased the complexity of the pp-CA1 potentials by adding volume-conducted currents due to the stimulation of the DG, and a second negative-going potential, due to the subsequent activation of the CA3 region (Figure 3). Severance of the Sc fibers neither changed the general appearance nor the response to increase in stimulation for the pp synapse. For all groups the I/O curves had similar characteristics (Sc-CA1 compared to pp-CA1 or Sc-cut for all stimulation intensities p > 0.05; Figure 3). Consequently the stimulation intensity used for plasticity experiments corresponded to the range of 100–250 μA (intensity of stimulation to elicit 40% of the maximum fEPSP slope) for all groups.

Bottom Line: We observed that field excitatory postsynaptic potentials at the pp-CA1 synapse have longer onset latencies and a shorter time-to-peak compared to the Sc-CA1 synapse.LTP (>24 h) was successfully evoked by tetanic afferent stimulation of pp-CA1 synapses.Paired-pulse responses also showed significant differences.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurophysiology, Medical Faculty, Ruhr University Bochum Bochum, Germany ; International Graduate School for Neuroscience, Ruhr University Bochum Bochum, Germany.

ABSTRACT
In terms of its sub-regional differentiation, the hippocampal CA1 region receives cortical information directly via the perforant (temporoammonic) path (pp-CA1 synapse) and indirectly via the tri-synaptic pathway where the last relay station is the Schaffer collateral-CA1 synapse (Sc-CA1 synapse). Research to date on pp-CA1 synapses has been conducted predominantly in vitro and never in awake animals, but these studies hint that information processing at this synapse might be distinct to processing at the Sc-CA1 synapse. Here, we characterized synaptic properties and synaptic plasticity at the pp-CA1 synapse of freely behaving adult rats. We observed that field excitatory postsynaptic potentials at the pp-CA1 synapse have longer onset latencies and a shorter time-to-peak compared to the Sc-CA1 synapse. LTP (>24 h) was successfully evoked by tetanic afferent stimulation of pp-CA1 synapses. Low frequency stimulation evoked synaptic depression at Sc-CA1 synapses, but did not elicit LTD at pp-CA1 synapses unless the Schaffer collateral afferents to the CA1 region had been severed. Paired-pulse responses also showed significant differences. Our data suggest that synaptic plasticity at the pp-CA1 synapse is distinct from the Sc-CA1 synapse and that this may reflect its specific role in hippocampal information processing.

No MeSH data available.


Related in: MedlinePlus