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Characteristics of spontaneous and evoked EPSPs recorded from dentate spiny hilar cells in rat hippocampal slices.
J Neurophysiol. 1993 Aug; 70(2):742-57.JN

Abstract

1. Excitation of the spiny subtype of hilar neurons in the fascia dentata was characterized by intracellular recording from hilar cells in hippocampal slices. Stimulation of the outer molecular layer was used to activate the perforant path. Evoked responses were examined, as well as the large spontaneous excitatory potentials that are a distinctive characteristic of spiny hilar cells. 2. Excitatory potentials that occurred spontaneously, as well as those that occurred in response to outer molecular layer stimulation, were similar among the cells that were sampled, regardless of morphological variations such as the presence or absence of thorny excrescences. Spontaneous and evoked excitatory postsynaptic potentials (EPSPs) were complex depolarizations that often had several discrete peaks. Spontaneous EPSPs increased in amplitude slightly with hyperpolarization, and evoked EPSPs clearly increased with hyperpolarization. 3. Applications of selective antagonists of excitatory amino acid receptors were used to determine which excitatory amino acid receptor mediates EPSPs of these cells. 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was used to block the receptor subtype selective for the agonists alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainic acid (the "AMPA/kainate" receptor). 2-amino-5-phosphonovaleric acid (APV) was used to block receptors specific for the agonist N-methyl-D-aspartate (NMDA; the "NMDA" receptor). Perfusion with CNQX (5-25 microM) completely blocked all spontaneous and evoked excitation, even when activity was examined at relatively depolarized membrane potentials and a low concentration of extracellular magnesium (0.5 mM) was used. Under these conditions, APV (25-50 microM) had no detectable effect on spontaneous activity but did increase the stimulus strength required to elicit responses to outer molecular layer stimulation. 4. When extracellular magnesium was lowered to 0 mM (nominally), there was strong evidence for a contribution of NMDA receptors to spontaneous and evoked EPSPs. Thus, when cells were perfused with 0 mM extracellular magnesium and 5 microM CNQX, spontaneous depolarizations were present and EPSPs could be triggered by stimulation of the outer molecular layer. Both the spontaneous and evoked EPSPs were blocked by 25 microM APV. 5. Because gamma-aminobutyric acid (GABA)A receptors can cause depolarizations in hippocampal neurons, the GABAA receptor antagonist bicuculline was used to determine whether some of the EPSPs were mediated by GABAergic neurons that are normally activated by spontaneous release of excitatory amino acids. Bicuculline (5-25 microM) had no effect on spontaneous depolarizations, and led to an enhancement of evoked depolarizations. Therefore it does not appear that GABAA receptor-mediated depolarizations contribute to hilar cell depolarizations.(

ABSTRACT

TRUNCATED AT 400 WORDS)

Authors+Show Affiliations

Neurology Research Center, Helen Hayes Hospital, New York State Department of Health, West Haverstraw 10993-1195.

Pub Type(s)

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

Language

eng

PubMed ID

8105038

Citation

Scharfman, H E.. "Characteristics of Spontaneous and Evoked EPSPs Recorded From Dentate Spiny Hilar Cells in Rat Hippocampal Slices." Journal of Neurophysiology, vol. 70, no. 2, 1993, pp. 742-57.
Scharfman HE. Characteristics of spontaneous and evoked EPSPs recorded from dentate spiny hilar cells in rat hippocampal slices. J Neurophysiol. 1993;70(2):742-57.
Scharfman, H. E. (1993). Characteristics of spontaneous and evoked EPSPs recorded from dentate spiny hilar cells in rat hippocampal slices. Journal of Neurophysiology, 70(2), 742-57.
Scharfman HE. Characteristics of Spontaneous and Evoked EPSPs Recorded From Dentate Spiny Hilar Cells in Rat Hippocampal Slices. J Neurophysiol. 1993;70(2):742-57. PubMed PMID: 8105038.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Characteristics of spontaneous and evoked EPSPs recorded from dentate spiny hilar cells in rat hippocampal slices. A1 - Scharfman,H E, PY - 1993/8/1/pubmed PY - 1993/8/1/medline PY - 1993/8/1/entrez SP - 742 EP - 57 JF - Journal of neurophysiology JO - J Neurophysiol VL - 70 IS - 2 N2 - 1. Excitation of the spiny subtype of hilar neurons in the fascia dentata was characterized by intracellular recording from hilar cells in hippocampal slices. Stimulation of the outer molecular layer was used to activate the perforant path. Evoked responses were examined, as well as the large spontaneous excitatory potentials that are a distinctive characteristic of spiny hilar cells. 2. Excitatory potentials that occurred spontaneously, as well as those that occurred in response to outer molecular layer stimulation, were similar among the cells that were sampled, regardless of morphological variations such as the presence or absence of thorny excrescences. Spontaneous and evoked excitatory postsynaptic potentials (EPSPs) were complex depolarizations that often had several discrete peaks. Spontaneous EPSPs increased in amplitude slightly with hyperpolarization, and evoked EPSPs clearly increased with hyperpolarization. 3. Applications of selective antagonists of excitatory amino acid receptors were used to determine which excitatory amino acid receptor mediates EPSPs of these cells. 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) was used to block the receptor subtype selective for the agonists alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and kainic acid (the "AMPA/kainate" receptor). 2-amino-5-phosphonovaleric acid (APV) was used to block receptors specific for the agonist N-methyl-D-aspartate (NMDA; the "NMDA" receptor). Perfusion with CNQX (5-25 microM) completely blocked all spontaneous and evoked excitation, even when activity was examined at relatively depolarized membrane potentials and a low concentration of extracellular magnesium (0.5 mM) was used. Under these conditions, APV (25-50 microM) had no detectable effect on spontaneous activity but did increase the stimulus strength required to elicit responses to outer molecular layer stimulation. 4. When extracellular magnesium was lowered to 0 mM (nominally), there was strong evidence for a contribution of NMDA receptors to spontaneous and evoked EPSPs. Thus, when cells were perfused with 0 mM extracellular magnesium and 5 microM CNQX, spontaneous depolarizations were present and EPSPs could be triggered by stimulation of the outer molecular layer. Both the spontaneous and evoked EPSPs were blocked by 25 microM APV. 5. Because gamma-aminobutyric acid (GABA)A receptors can cause depolarizations in hippocampal neurons, the GABAA receptor antagonist bicuculline was used to determine whether some of the EPSPs were mediated by GABAergic neurons that are normally activated by spontaneous release of excitatory amino acids. Bicuculline (5-25 microM) had no effect on spontaneous depolarizations, and led to an enhancement of evoked depolarizations. Therefore it does not appear that GABAA receptor-mediated depolarizations contribute to hilar cell depolarizations.(ABSTRACT TRUNCATED AT 400 WORDS) SN - 0022-3077 UR - https://www.unboundmedicine.com/medline/citation/8105038/Characteristics_of_spontaneous_and_evoked_EPSPs_recorded_from_dentate_spiny_hilar_cells_in_rat_hippocampal_slices_ L2 - https://journals.physiology.org/doi/10.1152/jn.1993.70.2.742?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -