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Published on: January 10, 2011
M-type potassium channels modulate Schaffer collateral-CA1 glutamatergic synaptic transmission.
1Department of Neurology, Box 800394, University of Virginia-HSC, Charlottesville, VA 22908, USA.
The Journal of Physiology
|June 8, 2012
Summary
M1 muscarinic receptor activation enhances glutamatergic transmission by inhibiting M-type potassium channels. This leads to increased presynaptic calcium influx and glutamate release in the hippocampus.
Area of Science:
- Neuroscience
- Synaptic Plasticity
- Molecular Pharmacology
Background:
- Muscarinic receptor activation influences glutamatergic transmission.
- M-type potassium channels are implicated in mediating muscarinic effects in the hippocampus.
- Previous research suggests M-type channels modulate glutamatergic synaptic transmission.
Purpose of the Study:
- To investigate if M1 muscarinic receptor activation enhances glutamatergic transmission.
- To determine if this enhancement occurs via M-type potassium channel inhibition in Schaffer collateral axons and terminals.
- To elucidate the role of M-type channels in presynaptic glutamate release.
Main Methods:
- Recording of miniature excitatory postsynaptic currents (mEPSCs) from CA1 pyramidal neurons.
- Application of M1 receptor agonist (McN-A-343), M-channel blockers (XE991, linopirdine), and M-channel opener (flupirtine).
- Current clamp recordings from CA3 pyramidal neurons to assess membrane potential and firing patterns.
- Experiments in calcium-free medium and with calcium channel blockers (P/Q- and N-type).
Main Results:
- M1 receptor activation and M-channel blockade increased mEPSC frequency, but not amplitude.
- M-channel opening decreased mEPSC frequency.
- The effect of M-channel blockade on mEPSCs was calcium-dependent.
- M1 receptor activation and M-channel blockade depolarized CA3 neurons and increased burst firing.
- Input resistance of CA3 neurons increased with M1 activation and M-channel blockade.
Conclusions:
- M1 muscarinic receptor activation inhibits M-type potassium channels in CA3 pyramidal neurons and Schaffer collaterals.
- This inhibition leads to depolarization, activation of voltage-gated calcium channels, and increased presynaptic glutamate release onto CA1 neurons.
- M-type potassium channels play a critical role in regulating presynaptic glutamate release modulated by muscarinic receptors.
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