A KDRT stop cassette (which also contains a single loxP site), followed by a 'smV5' tag (10 copies of Tag:V5 inserted into the backbone of a fluorescence dead GFP) that is flanked by GS linkers, has been inserted into the endogenous 5-HT2A locus in the third intracellular loop. This results in a conditionally tagged allele; KDR recombinase can be used to excise the KDRT cassette to produce 'smV5'-tagged 5-HT2A.