The objectives of this study were to characterize the ontogeny of the L-glutamate (glutamate) and N-methyl-D-aspartate (NMDA) binding sites in the developing guinea pig hippocampus, and to determine the effect of acute in vitro ethanol exposure on these binding sites. Specific [3H]glutamate binding and NMDA-sensitive [3H]glutamate binding were determined using a guinea pig hippocampal synaptic membrane preparation (HSMP). To characterize the ontogeny of the density (Bmax) and affinity (Kd) of the glutamate and NMDA binding sites, saturation analysis was conducted on HSMP of guinea pigs at gestational day (GD) 50 (immature fetus; term, GD 68), GD 62 (mature, near-term fetus), postnatal day (PD) 13 (neonate), and PD > 60 (adult). To examine the effect of ethanol on the glutamate and NMDA binding sites, HSMP of guinea pigs at GD 50, GD 62, PD 13, and PD > 60 was incubated with ethanol (0-100 mM), followed by determination of specific [3H]glutamate binding and NMDA-sensitive [3H]glutamate binding. To determine the effect of 50 mM ethanol on the Bmax and Kd of the glutamate and NMDA binding sites, HSMP of guinea pigs at GD 62 and PD > 60 was incubated with 0 or 50 mM ethanol followed by saturation analysis. The Bmax values of the hippocampal glutamate and NMDA binding sites were greater at GD 62 and PD 13 compared with GD 50 and PD > 60, but there was no change in the Kd of the binding sites throughout development.(ABSTRACT TRUNCATED AT 250 WORDS)