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Participation of low‐threshold calcium spikes in excitatory synaptic transmission in guinea pig medial frontal cortex
Author(s) -
De La Peña Elvira,
GeijoBarrientos Emilio
Publication year - 2000
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2000.00061.x
Subject(s) - excitatory postsynaptic potential , post tetanic potentiation , inhibitory postsynaptic potential , neuroscience , postsynaptic potential , neurotransmission , cnqx , chemistry , postsynaptic current , synaptic potential , membrane potential , biophysics , nmda receptor , biology , ampa receptor , biochemistry , receptor
We studied the activation of low‐threshold calcium spikes (LTS) by excitatory postsynaptic potentials in pyramidal neurons from guinea pig medial frontal cortex with intracellular recording. We used extracellular bicuculline and phaclofen and intracellular QX‐314 to block inhibitory synaptic potentials and sodium currents. Postsynaptic potentials were evoked by stimulation of layer I. We found that large (> 10–15 mV) excitatory synaptic potentials evoked from membrane potentials more negative than −75 mV were able to trigger LTS. The activation of LTS resulted in an increase of the rising slope or amplitude of the synaptic potentials depending on the size of the excitatory postsynaptic potential (EPSP). We used 100 μ m NiCl 2 to confirm the presence of LTS as part of the EPSPs. The N‐methyl‐ d ‐aspartate (NMDA) and non‐NMDA components of the excitatory synaptic potentials were isolated using (±)2‐amino‐5‐phosphonovaleric acid (APV; 50 μ m ) or 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX; 20 μ m ); both components could, independently, trigger an LTS. With recordings made with K + acetate‐filled electrodes, we show that the activation of LTS was critical to allow excitatory synaptic potentials to reach the threshold of action potential firing; also, this amplification of synaptic responses produced the firing of more than a single action potential by the postsynaptic cell. These results demonstrate that in cortical pyramidal neurons the activation of low‐threshold calcium spikes results in the amplification of synaptic responses.