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Cell-specific alterations in synaptic properties of hippocampal CA1 interneurons after kainate treatment.
J Neurophysiol. 1998 Dec; 80(6):2836-47.JN

Abstract

Cell-specific alterations in synaptic properties of hippocampal CA1 interneurons after kainate treatment. J. Neurophysiol. 80: 2836-2847, 1998. Hippocampal sclerosis and hyperexcitability are neuropathological features of human temporal lobe epilepsy that are reproduced in the kainic acid (KA) model of epilepsy in rats. To assess directly the role of inhibitory interneurons in the KA model, the membrane and synaptic properties of interneurons located in 1) stratum oriens near the alveus (O/A) and 2) at the border of stratum radiatum and stratum lacunosum-moleculare (LM), as well as those of pyramidal cells, were examined with whole cell recordings in slices of control and KA-lesioned rats. In current-clamp recordings, intrinsic cell properties such as action potential amplitude and duration, amplitude of fast and medium duration afterhyperpolarizations, membrane time constant, and input resistance were generally unchanged in all cell types after KA treatment. In voltage-clamp recordings, the amplitude and conductance of pharmacologically isolated excitatory postsynaptic currents (EPSCs) were significantly reduced in LM interneurons of KA-treated animals but were not significantly changed in O/A and pyramidal cells. The rise time of EPSCs was not significantly changed in any cell type after KA treatment. In contrast, the decay time constant of EPSCs was significantly faster in O/A interneurons of KA-treated rats but was unchanged in LM and pyramidal cells. The amplitude and conductance of pharmacologically isolated gamma-aminobutyric acid-A (GABAA) inhibitory postsynaptic currents (IPSCs) were not significantly changed in any cell type of KA-treated rats. The rise time and decay time constant of GABAA IPSCs were significantly faster in pyramidal cells of KA-treated rats but were not significantly changed in O/A and LM interneurons. These results suggest that complex alterations in synaptic currents occur in specific subpopulations of inhibitory interneurons in the CA1 region after KA lesions. A reduction of evoked excitatory drive onto inhibitory cells located at the border of stratum radiatum and stratum lacunosum-moleculare may contribute to disinhibition and polysynaptic epileptiform activity in the CA1 region. Compensatory changes, involving excitatory synaptic transmission on other interneuron subtypes and inhibitory synaptic transmission on pyramidal cells, may also take place and contribute to the residual, functional monosynaptic inhibition observed in principal cells after KA treatment.

Authors+Show Affiliations

Centre de Recherche en Sciences Neurologiques, Université de Montréal, Montréal, Québec H3C 3J7 Canada.No affiliation info availableNo affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

9862888

Citation

Morin, F, et al. "Cell-specific Alterations in Synaptic Properties of Hippocampal CA1 Interneurons After Kainate Treatment." Journal of Neurophysiology, vol. 80, no. 6, 1998, pp. 2836-47.
Morin F, Beaulieu C, Lacaille JC. Cell-specific alterations in synaptic properties of hippocampal CA1 interneurons after kainate treatment. J Neurophysiol. 1998;80(6):2836-47.
Morin, F., Beaulieu, C., & Lacaille, J. C. (1998). Cell-specific alterations in synaptic properties of hippocampal CA1 interneurons after kainate treatment. Journal of Neurophysiology, 80(6), 2836-47.
Morin F, Beaulieu C, Lacaille JC. Cell-specific Alterations in Synaptic Properties of Hippocampal CA1 Interneurons After Kainate Treatment. J Neurophysiol. 1998;80(6):2836-47. PubMed PMID: 9862888.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Cell-specific alterations in synaptic properties of hippocampal CA1 interneurons after kainate treatment. AU - Morin,F, AU - Beaulieu,C, AU - Lacaille,J C, PY - 1998/12/24/pubmed PY - 1998/12/24/medline PY - 1998/12/24/entrez SP - 2836 EP - 47 JF - Journal of neurophysiology JO - J Neurophysiol VL - 80 IS - 6 N2 - Cell-specific alterations in synaptic properties of hippocampal CA1 interneurons after kainate treatment. J. Neurophysiol. 80: 2836-2847, 1998. Hippocampal sclerosis and hyperexcitability are neuropathological features of human temporal lobe epilepsy that are reproduced in the kainic acid (KA) model of epilepsy in rats. To assess directly the role of inhibitory interneurons in the KA model, the membrane and synaptic properties of interneurons located in 1) stratum oriens near the alveus (O/A) and 2) at the border of stratum radiatum and stratum lacunosum-moleculare (LM), as well as those of pyramidal cells, were examined with whole cell recordings in slices of control and KA-lesioned rats. In current-clamp recordings, intrinsic cell properties such as action potential amplitude and duration, amplitude of fast and medium duration afterhyperpolarizations, membrane time constant, and input resistance were generally unchanged in all cell types after KA treatment. In voltage-clamp recordings, the amplitude and conductance of pharmacologically isolated excitatory postsynaptic currents (EPSCs) were significantly reduced in LM interneurons of KA-treated animals but were not significantly changed in O/A and pyramidal cells. The rise time of EPSCs was not significantly changed in any cell type after KA treatment. In contrast, the decay time constant of EPSCs was significantly faster in O/A interneurons of KA-treated rats but was unchanged in LM and pyramidal cells. The amplitude and conductance of pharmacologically isolated gamma-aminobutyric acid-A (GABAA) inhibitory postsynaptic currents (IPSCs) were not significantly changed in any cell type of KA-treated rats. The rise time and decay time constant of GABAA IPSCs were significantly faster in pyramidal cells of KA-treated rats but were not significantly changed in O/A and LM interneurons. These results suggest that complex alterations in synaptic currents occur in specific subpopulations of inhibitory interneurons in the CA1 region after KA lesions. A reduction of evoked excitatory drive onto inhibitory cells located at the border of stratum radiatum and stratum lacunosum-moleculare may contribute to disinhibition and polysynaptic epileptiform activity in the CA1 region. Compensatory changes, involving excitatory synaptic transmission on other interneuron subtypes and inhibitory synaptic transmission on pyramidal cells, may also take place and contribute to the residual, functional monosynaptic inhibition observed in principal cells after KA treatment. SN - 0022-3077 UR - https://www.unboundmedicine.com/medline/citation/9862888/Cell_specific_alterations_in_synaptic_properties_of_hippocampal_CA1_interneurons_after_kainate_treatment_ L2 - https://journals.physiology.org/doi/10.1152/jn.1998.80.6.2836?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -