Effects of acute ethanol exposure on glutamate release in the hippocampus of the fetal and adult guinea pig

The effects of in vitro and/or acute in vivo ethanol exposure on l-glutamate (GLU) release were determined in transverse hippocampal slices of the adult guinea pig and the immature and mature fetal guinea pig. In vitro ethanol (34–110 mM) exposure produced age-dependent and narrow concentration range-dependent depressant effects on K⁺-stimulated and basal GLU release, in which the fetal hippocampus was more sensitive than the adult. For acute in vivo ethanol exposure, the hippocampal slices were prepared 1 h after oral intubation of 4 g ethanol/kg body weight. In vivo ethanol exposure produced a persistent depressant effect on stimulated GLU release in the fetus and no effect in the adult. After acute in vivo ethanol treatment, in vitro ethanol (48 mM) exposure also decreased stimulated GLU release in the hippocampus of the immature and mature fetus and decreased basal GLU release only in the immature fetus. Furthermore, this acute in vivo/in vitro ethanol regimen did not affect stimulated or basal GLU release in the adult, which is indicative of tolerance development. Overall, the data indicate that ethanol depresses GLU release in the hippocampus of the guinea pig and that the fetal hippocampus is more susceptible to these depressant effects.