GABA(A)-dependent chloride influx modulates GABA(B)-mediated IPSPS in hippocampal pyramidal cells

Valeri Lopantsev, Philip A Schwartzkroin

Research output: Contribution to journalArticle

15 Scopus citations

Abstract

The relationship between postsynaptic inhibitory responses [the fast GABA(A)-mediated inhibitory postsynaptic potential (IPSP) and the slow GABA(B)-mediated IPSP] were investigated in hippocampal CA3 pyramidal cells. Mossy fiber-evoked GABA(B)-mediated IPSPs were, paradoxically, of greater amplitude in cells with resting membrane potential of -62 mV (13.6 ± 0.5 mV; mean ± SE) as compared with cells with resting membrane potential of -54 mV (7.0 ± 0.8 mV). In addition, when a cell's membrane potential was artificially manipulated, GABA(B)-mediated IPSPs were reduced at relatively depolarized levels (-55 mV) and enhanced at relatively hyperpolarized potentials (at least -60 mV). In contrast, the preceding GABA(A)-mediated IPSPs were larger at the more positive membrane potentials and smaller as the cell was hyperpolarized. Similar voltage dependency was obtained when monosynaptic GABA(A)- and GABA(B)-mediated IPSPs were isolated in the presence of glutamatergic receptor antagonists. However, monosynaptic GABA(B)-mediated IPSPs isolated in the presence of glutamatergic and GABA(A) receptor antagonists were not reduced at the more positive membrane potentials, and were significantly larger in amplitude than GABA(B)-mediated IPSPs preceded by a monosynaptic GABA(A)-mediated IPSP. The amplitude of the isolated monosynaptic GABA(B)-mediated IPSPs recorded with potassium chloride-containing microelectrodes was significantly smaller than the comparable potential recorded with potassium acetate microelectrodes without chloride. We conclude that voltage-dependent chloride influx, via GABA(A) receptor-gated channels, modulates postsynaptic GABA(B)-mediated inhibition in hippocampal CA3 pyramidal cells.

Original languageEnglish (US)
Pages (from-to)1218-1223
Number of pages6
JournalJournal of Neurophysiology
Volume82
Issue number3
StatePublished - 1999
Externally publishedYes

ASJC Scopus subject areas

  • Physiology
  • Neuroscience(all)

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