Blocking GABAA inhibition reveals AMPA- and NMDA-receptor-mediated polysynaptic responses in the CA1 region of the rat hippocampus

Abstract

inhibition reveals AMPA- and NMDA-receptor-mediated polysyn- observations suggest that a similar activity may develop unaptic responses in the CA1 region of the rat hippocampus. J. Neu- der certain conditions. First, although less developed than rophysiol. 77: 2071–2082, 1997. We have investigated the condi- in the CA3 region, excitatory recurrent connections between tions required to evoke polysynaptic responses in the isolated CA1 pyramidal cells have been described (Deuchars and Thomregion of hippocampal slices from Wistar adult rats. Experiments were performed with extracellular and whole cell recording tech- son 1996; Thomson and Radpour 1991). Second, a-aminoniques. In the presence of bicuculline (10 mM), 6-cyano-7-nitro- 3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-quinoxaline-2-3-dione (10 mM), glycine (10 mM), and a low exand/or N-methyl-D-aspartate (NMDA)-receptor-mediated ternal concentration of Mg burst have been recorded after blockade of g-aminobutyric 2 / (0.3 mM), electrical stimulation of the Schaffer collaterals/commissural pathway evoked graded N- acid-A (GABAA) (Dingledine et al. 1986; Williamson and methyl-D-aspartate (NMDA)-receptor-mediated late field poten- Wheal 1992) or adenosine A1 receptors (in low external tials in the stratum radiatum of the CA1 region. These responses Mg 2 / conditions) (Klishin et al. 1995). However, it rewere generated via polysynaptic connections because their latency mained unclear if these events are polysynaptic and if the