We previously found that ethanol inhibits muscarinic receptor-induced proliferation of rat cortical astrocytes and human astrocytoma cells and suggested this as a possible mechanism involved in its developmental neurotoxicity. We also observed that, though several signal transduction pathways are relevant for carbachol-induced cell proliferation, activation of PKC zeta and p70S6 kinase is selectively inhibited by low concentrations of ethanol. In the present study we used fetal human astrocytes to expand these findings to a direct target of ethanol in humans. Astrocyte cultures, deriving from legally aborted fetuses, were stained for GFAP and shown to be 90-95% pure. Carbachol induced increases in [(3)H]thymidine and BrdU incorporation in synchronized cells. Carbachol-induced DNA synthesis was strongly inhibited by ethanol. Carbachol also induced phosphorylation of (Thr410)PKC zeta, (Ser473)Akt, and (Thr389)p70S6 kinase, and ethanol (50 mM) inhibited phosphorylation of PKC zeta and p70S6 kinase, but not of Akt. These results expand previous findings in rat astrocytes and human astrocytoma cells and suggest that intracellular signal transduction pathways activated by muscarinic receptors may represent a relevant target for the developmental neurotoxicity of ethanol in humans.