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Published on: March 20, 2014
High affinity group III mGluRs regulate mossy fiber input to CA3 interneurons
Kathleen E Cosgrove1, Stephen D Meriney, Germán Barrionuevo
1Department of Neuroscience, University of Pittsburgh, Pittsburgh, PA 15260, USA.
Group III metabotropic glutamate receptors (mGluRs) 4/8 activation on mossy fiber terminals regulates the timing and probability of action potentials in hippocampal stratum lacunosum-moleculare interneurons (L-Mi). This presynaptic mechanism fine-tunes feedforward inhibition in the CA3 region.
Area of Science:
- Neuroscience
- Molecular Biology
- Cellular Physiology
Background:
- Stratum lacunosum-moleculare interneurons (L-Mi) in hippocampal area CA3 provide feedforward inhibition to pyramidal cells.
- Presynaptic metabotropic glutamate receptors (mGluRs) modulate neurotransmitter release.
- Group III mGluRs are implicated in regulating synaptic transmission.
Purpose of the Study:
- To investigate the role of group III mGluRs (4/8) in modulating glutamate release from hippocampal mossy fiber (MF) terminals onto L-Mi.
- To elucidate the mechanisms underlying mGluR-mediated regulation of MF synaptic transmission.
Main Methods:
- Selective activation of group III mGluRs using L-ளு-2-amino-4-phosphonobutyric acid (L-AP4).
- Measurement of MF excitatory postsynaptic currents (EPSCs) in L-Mi.
- Pharmacological manipulation using mGluR antagonists (MSOP) and assessment of N-type voltage-gated calcium channels.
Main Results:
- Activation of mGluRs 4/8 by L-AP4 decreased glutamate release probability from MF terminals.
- L-AP4 application reduced asynchronous MF EPSC frequency.
- Antagonist application revealed that mGluRs 4/8 are not tonically active but regulate firing probability and delay L-Mi action potential initiation.
Conclusions:
- Presynaptic group III mGluRs 4/8 activation fine-tunes the probability and timing of action potential firing in L-Mi.
- This regulation occurs via modulation of glutamate release from MF terminals, involving N-type voltage-gated calcium channels.
- mGluR 4/8 activation delays L-Mi firing, impacting feedforward inhibition in the hippocampal CA3 region.
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