Immunohistologic analysis of coronal sections of adult mice using antibodies against the HA tag of the transgene-derived human KCNB1 and against a conserved C-terminal epitope common to mouse and human KCNB1 demonstrate expression of transgenic and total (mouse and human in transgenic or mouse only in control mice) KCNB1 in the cortex and hippocampus, but not other brain regions. Both antibodies reveal clustered KCNB1 channels in plasma membranes of cortical and hippocampal neurons. Densitometric analysis of immunoblots of brain lysates probed with the non-specific antibody shows that transgenic brains contain approximately approximately 1.5-fold the number of channels present in non-transgenic control lysates, or half as many transgene-derived as endogenous channels. (J:260029)