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Hippocampal CA1 lacunosum-moleculare interneurons: modulation of monosynaptic GABAergic IPSCs by presynaptic GABAB receptors.
J Neurophysiol. 1995 Nov; 74(5):2126-37.JN

Abstract

1. Whole cell patch-clamp recordings were employed to characterize monosynaptic inhibitory postsynaptic currents (IPSCs) in morphologically and electrophysiologically identified interneurons located in the stratum lacunosum moleculare, or near the border of the stratum radiatum (LM interneurons), in the CA1 region of hippocampal slices taken from 3- to 4-wk-old rats. Monosynaptic IPSCs, evoked in the presence of glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 20 microM) and D-2-amino-5-phosphopentanoate (APV; 50 microM) were biphasic. The gamma-aminobutyric acid-A (GABAA) receptor antagonist, bicuculline (20 microM), blocked the fast IPSC, and the slow IPSC was blocked by the GABAB receptor antagonist CGP35348 (500 microM). 2. Monosynaptic IPSCs were evoked by electrical stimulation in several distant regions including the stratum radiatum, the stratum oriens, the stratum lacunosum-moleculare, and the molecular layer of dentate gyrus, suggesting an extensive network of inhibitory interneurons in the hippocampus. In paired recordings of CA1 interneurons and pyramidal cells, IPSCs were evoked by electrical stimulation of most of these distal regions with the exception of the molecular layer of dentate gyrus, which evoked an IPSC only in LM interneurons. 3. Frequent (> 0.1 Hz) stimulation depressed the evoked IPSCs. With a paired-pulse protocol, the second IPSC was depressed and the maximal depression (40-50%) was observed with an interstimulus interval of 100-200 ms. 4. The GABAB receptor agonist baclofen (1 microM) reduced the amplitude of evoked IPSCs and the paired-pulse depression of the second IPSC. The GABAB receptor antagonist CGP35348 (0.5-1 mM) had no significant effect on the amplitude of isolated IPSCs. However, CGP35348 reduced but did not fully block paired-pulse depression, suggesting that this depression is partly due to the activation of presynaptic GABAB receptors. 5. The paired-pulse depression depended on the level of transmitter release. Potentiation of synaptic release of GABA, by increasing the extracellular Ca2+ concentration to 4 mM and reducing the extracellular Mg2+ concentration to 0.1 mM, enhanced the depression. Reduction of transmitter release by increasing extracellular Mg2+ concentration to 7 mM diminished the paired-pulse depression of IPSCs. After potentiation of transmitter release, CGP35348 was less efficient in reducing the paired-pulse depression, suggesting that enhancement of depression by high-calcium/low-magnesium medium was preferentially due to the potentiation of a GABAB-independent component. 6. In summary, monosynaptic IPSCs recorded in LM interneurons show similar features to those recorded in pyramidal cells. The strong correlation between the level of transmitter release and the degree of paired-pulse depression may have important physiological consequences, because in synapses with a high level of activity and a high level of GABA release, inhibition is powerful, but depression can develop more readily.

Authors+Show Affiliations

Institut National de la Santé et de la Recherche Médicale Unité 29, Paris, France.No affiliation info availableNo affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

8592201

Citation

Khazipov, R, et al. "Hippocampal CA1 Lacunosum-moleculare Interneurons: Modulation of Monosynaptic GABAergic IPSCs By Presynaptic GABAB Receptors." Journal of Neurophysiology, vol. 74, no. 5, 1995, pp. 2126-37.
Khazipov R, Congar P, Ben-Ari Y. Hippocampal CA1 lacunosum-moleculare interneurons: modulation of monosynaptic GABAergic IPSCs by presynaptic GABAB receptors. J Neurophysiol. 1995;74(5):2126-37.
Khazipov, R., Congar, P., & Ben-Ari, Y. (1995). Hippocampal CA1 lacunosum-moleculare interneurons: modulation of monosynaptic GABAergic IPSCs by presynaptic GABAB receptors. Journal of Neurophysiology, 74(5), 2126-37.
Khazipov R, Congar P, Ben-Ari Y. Hippocampal CA1 Lacunosum-moleculare Interneurons: Modulation of Monosynaptic GABAergic IPSCs By Presynaptic GABAB Receptors. J Neurophysiol. 1995;74(5):2126-37. PubMed PMID: 8592201.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Hippocampal CA1 lacunosum-moleculare interneurons: modulation of monosynaptic GABAergic IPSCs by presynaptic GABAB receptors. AU - Khazipov,R, AU - Congar,P, AU - Ben-Ari,Y, PY - 1995/11/1/pubmed PY - 1995/11/1/medline PY - 1995/11/1/entrez SP - 2126 EP - 37 JF - Journal of neurophysiology JO - J Neurophysiol VL - 74 IS - 5 N2 - 1. Whole cell patch-clamp recordings were employed to characterize monosynaptic inhibitory postsynaptic currents (IPSCs) in morphologically and electrophysiologically identified interneurons located in the stratum lacunosum moleculare, or near the border of the stratum radiatum (LM interneurons), in the CA1 region of hippocampal slices taken from 3- to 4-wk-old rats. Monosynaptic IPSCs, evoked in the presence of glutamate receptor antagonists 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 20 microM) and D-2-amino-5-phosphopentanoate (APV; 50 microM) were biphasic. The gamma-aminobutyric acid-A (GABAA) receptor antagonist, bicuculline (20 microM), blocked the fast IPSC, and the slow IPSC was blocked by the GABAB receptor antagonist CGP35348 (500 microM). 2. Monosynaptic IPSCs were evoked by electrical stimulation in several distant regions including the stratum radiatum, the stratum oriens, the stratum lacunosum-moleculare, and the molecular layer of dentate gyrus, suggesting an extensive network of inhibitory interneurons in the hippocampus. In paired recordings of CA1 interneurons and pyramidal cells, IPSCs were evoked by electrical stimulation of most of these distal regions with the exception of the molecular layer of dentate gyrus, which evoked an IPSC only in LM interneurons. 3. Frequent (> 0.1 Hz) stimulation depressed the evoked IPSCs. With a paired-pulse protocol, the second IPSC was depressed and the maximal depression (40-50%) was observed with an interstimulus interval of 100-200 ms. 4. The GABAB receptor agonist baclofen (1 microM) reduced the amplitude of evoked IPSCs and the paired-pulse depression of the second IPSC. The GABAB receptor antagonist CGP35348 (0.5-1 mM) had no significant effect on the amplitude of isolated IPSCs. However, CGP35348 reduced but did not fully block paired-pulse depression, suggesting that this depression is partly due to the activation of presynaptic GABAB receptors. 5. The paired-pulse depression depended on the level of transmitter release. Potentiation of synaptic release of GABA, by increasing the extracellular Ca2+ concentration to 4 mM and reducing the extracellular Mg2+ concentration to 0.1 mM, enhanced the depression. Reduction of transmitter release by increasing extracellular Mg2+ concentration to 7 mM diminished the paired-pulse depression of IPSCs. After potentiation of transmitter release, CGP35348 was less efficient in reducing the paired-pulse depression, suggesting that enhancement of depression by high-calcium/low-magnesium medium was preferentially due to the potentiation of a GABAB-independent component. 6. In summary, monosynaptic IPSCs recorded in LM interneurons show similar features to those recorded in pyramidal cells. The strong correlation between the level of transmitter release and the degree of paired-pulse depression may have important physiological consequences, because in synapses with a high level of activity and a high level of GABA release, inhibition is powerful, but depression can develop more readily. SN - 0022-3077 UR - https://www.unboundmedicine.com/medline/citation/8592201/Hippocampal_CA1_lacunosum_moleculare_interneurons:_modulation_of_monosynaptic_GABAergic_IPSCs_by_presynaptic_GABAB_receptors_ L2 - https://journals.physiology.org/doi/10.1152/jn.1995.74.5.2126?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -