Physostigmine and memantine stimulation converge on serine-phosphorylation of GSK3 in mouse brain. Mice were treated with physostigmine (0.4 mg/kg; 15 min), memantine (50 mg/kg; 2 h), or both drugs (physostigmine was given 105 min after memantine, for 15 min), and protein extracts from the hippocampus, cerebral cortex, and striatum were immunoblotted with antibodies for phospho-Ser21-GSK3α, phospho-Ser9-GSK3β, total GSK3α/β, and phospho-Tyr279/216-GSK3α/β. Quantitative values were obtained by densitometric scans of immunoblots (means ± S.E.M.; n=4). No statistical differences (p > 0.05) were observed comparing the results from treatment with physostigmine alone to those following treatment with memantine plus physostigmine.