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Rapid kinetics and inward rectification of miniature EPSCs in layer I neurons of rat neocortex.
J Neurophysiol. 1997 May; 77(5):2416-26.JN

Abstract

With the use of the whole cell patch-clamp technique combined with visualization of neurons in brain slices, we studied the properties of miniature excitatory postsynaptic currents (mEPSCs) in rat neocortical layer I neurons. At holding potentials (-50 to -70 mV) near the resting membrane potential (RMP), mEPSCs had amplitudes of 5-100 pA and were mediated mostly by alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA) receptors. Amplitude histograms were skewed toward large events. An N-methyl-D-aspartate (NMDA) component was revealed by depolarization to -30 mV or by the use of a Mg2+-free bathing solution. At RMP, averaged AMPA mEPSCs had a 10-90% rise time of approximately 0.3 ms (uncorrected for instrument filtering). The decay of averaged mEPSCs was best fit by double-exponential functions in most cases. The fast, dominating component had a decay time constant of approximately 1.2 ms and comprised approximately 80% of the total amplitude. A small slow component had a decay time constant of approximately 4 ms. Positive correlations were found between rise and decay times of both individual and averaged mEPSCs, indicative of dendritic filtering. Some large-amplitude mEPSCs and spontaneous EPSCs (recorded in the absence of tetrodotoxin) had slower kinetics, suggesting a role of asynchronous transmitter release in shaping EPSCs. The amplitudes of mEPSCs were much smaller at +60 mV than at -60 mV, indicating that synaptic AMPA-receptor-mediated currents were inwardly rectifying. These results suggest that neocortical layer I neurons receive both NMDA- and AMPA-receptor-mediated synaptic inputs. The rapid decay of EPSCs appears to be largely determined by AMPA receptor deactivation. The observed rectification of synaptic responses suggests that synaptic AMPA receptors in layer I neurons may lack GluR-2 subunits and may be Ca2+ permeable.

Authors+Show Affiliations

Neurobiology Research Center and Department of Physiology and Biophysics, University of Alabama at Birmingham, 35294, USA.No affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, Non-P.H.S.
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9163367

Citation

Zhou, F M., and J J. Hablitz. "Rapid Kinetics and Inward Rectification of Miniature EPSCs in Layer I Neurons of Rat Neocortex." Journal of Neurophysiology, vol. 77, no. 5, 1997, pp. 2416-26.
Zhou FM, Hablitz JJ. Rapid kinetics and inward rectification of miniature EPSCs in layer I neurons of rat neocortex. J Neurophysiol. 1997;77(5):2416-26.
Zhou, F. M., & Hablitz, J. J. (1997). Rapid kinetics and inward rectification of miniature EPSCs in layer I neurons of rat neocortex. Journal of Neurophysiology, 77(5), 2416-26.
Zhou FM, Hablitz JJ. Rapid Kinetics and Inward Rectification of Miniature EPSCs in Layer I Neurons of Rat Neocortex. J Neurophysiol. 1997;77(5):2416-26. PubMed PMID: 9163367.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Rapid kinetics and inward rectification of miniature EPSCs in layer I neurons of rat neocortex. AU - Zhou,F M, AU - Hablitz,J J, PY - 1997/5/1/pubmed PY - 1997/5/1/medline PY - 1997/5/1/entrez SP - 2416 EP - 26 JF - Journal of neurophysiology JO - J Neurophysiol VL - 77 IS - 5 N2 - With the use of the whole cell patch-clamp technique combined with visualization of neurons in brain slices, we studied the properties of miniature excitatory postsynaptic currents (mEPSCs) in rat neocortical layer I neurons. At holding potentials (-50 to -70 mV) near the resting membrane potential (RMP), mEPSCs had amplitudes of 5-100 pA and were mediated mostly by alpha-amino-3-hydroxy-5-methyl-4-isoxazoleproprionate (AMPA) receptors. Amplitude histograms were skewed toward large events. An N-methyl-D-aspartate (NMDA) component was revealed by depolarization to -30 mV or by the use of a Mg2+-free bathing solution. At RMP, averaged AMPA mEPSCs had a 10-90% rise time of approximately 0.3 ms (uncorrected for instrument filtering). The decay of averaged mEPSCs was best fit by double-exponential functions in most cases. The fast, dominating component had a decay time constant of approximately 1.2 ms and comprised approximately 80% of the total amplitude. A small slow component had a decay time constant of approximately 4 ms. Positive correlations were found between rise and decay times of both individual and averaged mEPSCs, indicative of dendritic filtering. Some large-amplitude mEPSCs and spontaneous EPSCs (recorded in the absence of tetrodotoxin) had slower kinetics, suggesting a role of asynchronous transmitter release in shaping EPSCs. The amplitudes of mEPSCs were much smaller at +60 mV than at -60 mV, indicating that synaptic AMPA-receptor-mediated currents were inwardly rectifying. These results suggest that neocortical layer I neurons receive both NMDA- and AMPA-receptor-mediated synaptic inputs. The rapid decay of EPSCs appears to be largely determined by AMPA receptor deactivation. The observed rectification of synaptic responses suggests that synaptic AMPA receptors in layer I neurons may lack GluR-2 subunits and may be Ca2+ permeable. SN - 0022-3077 UR - https://www.unboundmedicine.com/medline/citation/9163367/Rapid_kinetics_and_inward_rectification_of_miniature_EPSCs_in_layer_I_neurons_of_rat_neocortex_ L2 - https://journals.physiology.org/doi/10.1152/jn.1997.77.5.2416?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -