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Published on: July 31, 2013
Cholinergic modulation of excitatory synaptic input integration in hippocampal CA1
1Department of Anatomy and Neurobiology, Virginia Commonwealth University, Richmond, VA 23298, USA. amcquiston@vcu.edu
The Journal of Physiology
|August 10, 2010
Summary
Perforant path (PP) inputs can enhance or suppress Schaffer collateral (SC) inputs in the hippocampus during theta rhythms. This gating effect is modulated by acetylcholine and GABA(B) receptors, impacting neuronal firing.
Area of Science:
- Neuroscience
- Neurophysiology
- Hippocampal Circuitry
Background:
- Hippocampal CA1 neurons receive inputs from the entorhinal cortex (perforant path, PP) and CA3 (Schaffer collaterals, SCs).
- Theta rhythms orchestrate the timing of these inputs, occurring during elevated acetylcholine levels.
- Understanding how PP inputs modulate SC inputs under cholinergic influence is crucial for hippocampal function.
Purpose of the Study:
- To investigate the effect of perforant path (PP) inputs on Schaffer collateral (SC) inputs in hippocampal CA1.
- To determine the role of cholinergic receptor activation in modulating this interaction.
- To elucidate the temporal dynamics of PP-SC input integration within a theta cycle.
Main Methods:
- Utilized voltage-sensitive dye imaging, field excitatory postsynaptic potentials (fEPSPs), and whole-cell patch clamping in rat hippocampal slices.
- Stimulated the stratum lacunosum-moleculare (SLM, containing PP) and stratum radiatum (SR, containing SC) at varying intervals.
- Administered carbachol (cholinergic agonist) and specific receptor antagonists (atropine, CGP 54626) to assess modulation.
Main Results:
- Short-interval SLM stimulation (25-75 ms before SR) caused excitatory event summation, unaffected by carbachol.
- Long-interval SLM stimulation (150-225 ms before SR) induced suppression, augmented by carbachol and blocked by atropine and CGP 54626.
- Carbachol increased action potential firing probability, which was counteracted by long-interval SLM prepulses.
Conclusions:
- Hippocampal CA1 integrates PP and SC inputs differentially based on their temporal relationship within a theta cycle.
- Feedforward inhibition mediated by SLM inputs plays a critical role in gating SC-driven excitation.
- Cholinergic and GABA(B) receptor systems modulate this inhibitory gating, influencing neuronal excitability and information processing.
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