| 11600631 |
Gonzalez-Burgos G, Barrionuevo G: Voltage-gated sodium channels shape subthreshold EPSPs in layer 5 pyramidal neurons from rat prefrontal cortex. J Neurophysiol. 2001 Oct;86(4):1671-84.
The role of voltage-dependent channels in shaping subthreshold excitatory postsynaptic potentials (EPSPs) in neocortical layer 5 pyramidal neurons from rat medial prefrontal cortex (PFC) was investigated using patch-clamp recordings from visually identified neurons in brain slices. Small-amplitude EPSPs evoked by stimulation of superficial layers were not affected by the N-methyl-D-aspartate receptor antagonist D-2-amino-5-phosphonopentanoic acid but were abolished by the AMPA receptor antagonist 6-cyano-7-nitroquinoxalene-2,3-dione, suggesting that they were primarily mediated by AMPA receptors. AMPA receptor-mediated EPSPs (AMPA-EPSPs) evoked in the apical dendrites were markedly enhanced, or increased in peak and duration, at depolarized holding potentials. Enhancement of AMPA-EPSPs was reduced by loading the cells with lidocaine N-ethylbromide (QX-314) and by local application of the Na (+) channel blocker tetrodotoxin (TTX) to the soma but not to the middle/proximal apical dendrite. In contrast, blockade of Ca (2+) channels by co-application of Cd (2+) and Ni (2+) to the soma or apical dendrite did not affect the AMPA-EPSPs. Like single EPSPs, EPSP trains were shaped by Na (+) but not Ca (2+) channels. EPSPs simulated by injecting synaptic-like current into proximal/middle apical dendrite (simEPSPs) were enhanced at depolarized holding potentials similarly to AMPA-EPSPs. Extensive blockade of Ca (2+) channels by bath application of the Cd (2+) and Ni (2+) mixture had no effects on simEPSPs, whereas bath-applied TTX removed the depolarization-dependent EPSP amplification. Inhibition of K (+) currents by 4-aminopyridine (4-AP) and TEA increased the TTX-sensitive EPSP amplification. Moreover, strong inhibition of K (+) currents by high concentrations of 4-AP and TEA revealed a contribution of Ca (2+) channels to EPSPs that, however, seemed to be dependent on Na (+) channel activation. Our results indicate that in layer 5 pyramidal neurons from PFC, Na (+), and K (+) voltage-gated channels shape EPSPs within the voltage range that is subthreshold for somatic action potentials. |
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