The transgene is comprised of a minimal immediate-early CMV enhancer/chicken beta-actin promoter driving ubiquitous expression of a lox-P flanked beta-galactosidase/neomycin phosphotransferase II (beta-geo) fusion gene that terminates in a strong, triple polyadenylation signal, followed by a C-terminally truncated wheat germ agglutinin coding sequence. Neuron-specific excision of the beta-geo gene by cre recombinase permits expression of the lectin, whose migration allows tracing of synapses involving the expressing cells. (J:92042)