A rat cDNA containing exons 6 through 10, which encodes the 'c' isoform, followed by a floxed neo cassette was inserted in frame with exon 5 and replaced alternative exons for the immediate-early isoforms 'a' and 'Ania3'. The absence of the 'a' isoform was confirmed by western blot analysis following induction of expression by maximal electroconvulsive seizure. Expression of the 'b' and 'c' isoform is normal. (J:174500)