TY - JOUR
T1 - GABAA-dependent chloride influx modulates reversal potential of GABAB-mediated IPSPs in hippocampal pyramidal cells
AU - Lopantsev, Valeri
AU - Schwartzkroin, Philip A
PY - 2001
Y1 - 2001
N2 - Changes in intracellular chloride concentration, mediated by chloride influx through GABAA receptor-gated channels, may modulate GABAB receptor-mediated inhibitory postsynaptic potentials (GABAB IPSPs) via unknown mechanisms. Recording from CA3 pyramidal cells in hippocampal slices, we investigated the impact of chloride influx during GABAA receptor-mediated IPSPs (GABAA IPSPs) on the properties of GABAB IPSPs. At relatively positive membrane potentials (near -55 mV), mossy fiber-evoked GABAB IPSPs were reduced (compared with their magnitude at -60 mV) when preceded by GABAA receptor-mediated chloride influx. This effect was not associated with a correlated reduction in membrane permeability during the GABAB IPSP. The mossy fiber-evoked GABAB IPSP showed a positive shift in reversal potential (from -99 to -93 mV) when it was preceded by a GABAA IPSP evoked at cell membrane potential of -55 mV as compared with -60 mV. Similarly, when intracellular chloride concentration was raised via chloride diffusion from an intracellular microelectrode, there was a reduction of the pharmacologically isolated monosynaptic GABAB IPSP and a concurrent shift of GABAB IPSP reversal potential from -98 to -90 mV. We conclude that in hippocampal pyramidal cells, in which "resting" membrane potential is near action potential threshold, chloride influx via GABAA IPSPs shifts the reversal potential of subsequent GABAB receptor-mediated postsynaptic responses in a positive direction and reduces their magnitude.
AB - Changes in intracellular chloride concentration, mediated by chloride influx through GABAA receptor-gated channels, may modulate GABAB receptor-mediated inhibitory postsynaptic potentials (GABAB IPSPs) via unknown mechanisms. Recording from CA3 pyramidal cells in hippocampal slices, we investigated the impact of chloride influx during GABAA receptor-mediated IPSPs (GABAA IPSPs) on the properties of GABAB IPSPs. At relatively positive membrane potentials (near -55 mV), mossy fiber-evoked GABAB IPSPs were reduced (compared with their magnitude at -60 mV) when preceded by GABAA receptor-mediated chloride influx. This effect was not associated with a correlated reduction in membrane permeability during the GABAB IPSP. The mossy fiber-evoked GABAB IPSP showed a positive shift in reversal potential (from -99 to -93 mV) when it was preceded by a GABAA IPSP evoked at cell membrane potential of -55 mV as compared with -60 mV. Similarly, when intracellular chloride concentration was raised via chloride diffusion from an intracellular microelectrode, there was a reduction of the pharmacologically isolated monosynaptic GABAB IPSP and a concurrent shift of GABAB IPSP reversal potential from -98 to -90 mV. We conclude that in hippocampal pyramidal cells, in which "resting" membrane potential is near action potential threshold, chloride influx via GABAA IPSPs shifts the reversal potential of subsequent GABAB receptor-mediated postsynaptic responses in a positive direction and reduces their magnitude.
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M3 - Article
C2 - 11387384
AN - SCOPUS:0035006102
VL - 85
SP - 2381
EP - 2387
JO - Journal of Neurophysiology
JF - Journal of Neurophysiology
SN - 0022-3077
IS - 6
ER -