D-aminophosphonovaleric acid-sensitive spontaneous giant EPSPs in immature rat hippocampal neurones.

N-Methyl-D-aspartate (NMDA)-receptor acuvation in both hippocampus and wsual cortex of adult animals is involved m long-term changes m synaptic transmission. These synaptlc modifications are thought to be triggered by calcium fluxes through the NMDA-activated channel. Recent experiments also suggest that NMDA-receptor activation plays a crucial role during critical periods of development (Kleinschnudt et al., 1987: Tsumoto et al., 1987). We now report the presence of spontaneous, recurrent, network-driven grant EPSPs which were blocked by the selective NMDA-receptor antagorests, D-aminophosphonovaleric acid (D-APV) and (+)-3-(2-carboxyplperazin-4-yl)-propyl-1phosphonic acid (CPP), in the CA3 regxon of hippocampal shces taken from rats 0-14 days old. Fully submerged transverse hippocampal slices (500-600 /tm) were superfused at 35°C, with oxygenated artificml cerebrospinal fluid of the following composition (mM): NaC1 126, KCI 3.5, CaC12 2, MgCI 2 1.3; NaH2PO4 1.4, NaHCO 3 25 and glucose 11 (Gho et al., 1986). Intracellular recordings were made from CA3 pyramidal cells by means of KCl-filled electrodes (3 M, 40-60 M~2). The potentials, amplified, were displayed on a computer-driven chart recorder. Spontaneous, recurrent bursts were observed in 46 out of 58 cells (79%) during the first post-natal week (fig. 1A,B). These bursts consisted of de-