AP-1-like DNA-binding activity in wild-type andfosB−/− mouse hippocampus after kainic acid treatment. Autoradiogram of a gel mobility shift assay showing AP-1-like DNA-binding activity in hippocampal nuclear extracts under control (con) conditions, and 4 hr and 5 d after a single kainate injection. Lane 4 represents a supershift of the 5 d sample using a FosB-selective antiserum. Thearrows indicate the position of the lowest AP-1 band that is selectively shifted by the FosB antiserum and that is absent infosB−/− mice.