Effects of ethanol exposure in utero on Cajal-Retzius cells in the developing cortex.

BACKGROUND: Prenatal exposure to ethanol exerts teratogenic effects on the developing brain. Here, we tested the hypothesis that exposure to ethanol in utero alters the disposition of Cajal-Retzius cells that play a key role in orchestrating proliferation, migration, and laminar integration of cortical neurons in the embryonic cortex.
METHODS: Pregnant Ebf2-EGFP mice, harboring EGFP-fluorescent Cajal-Retzius cells, were subjected to a 2% w/w ethanol consumption regimen starting at neural tube closure and lasting throughout gestation. Genesis of Cajal-Retzius cells was assessed by means of 5-bromo-2-deoxyuridine (BrdU) immunofluorescence at embryonic day 12.5, their counts and distribution were determined between postnatal day (P)0 and P4, patch clamp electrophysiology was performed between P2 and P3 to analyze GABA-mediated synaptic activity, and open-field behavioral testing was conducted in P45-P50 adolescents.
RESULTS: In Ebf2-EGFP embryos exposed to ethanol in utero, we found increased BrdU labeling and expanded distribution of Cajal-Retzius cells in the cortical hem, pointing to increased genesis and proliferation. Postnatally, we found an increase in Cajal-Retzius cell number in cortical layer I. In addition, they displayed altered patterning of spontaneous GABA-mediated synaptic barrages and enhanced GABA-mediated synaptic activity, suggesting enhanced GABAergic tone.
CONCLUSIONS: These findings, together, underscore that Cajal-Retzius cells contribute to the ethanol-induced aberration of cortical development and abnormal GABAergic neurotransmission at the impactful time when intracortical circuits form.