Figure 2.

Generation of horizontal cell-specific D1R knock-out mouse. A, Strategy for generating D1R^{β-gal/β-gal} and D1R^flox/flox mouse lines: (i) a DNA cassette encoding both FRT-flanked sequence of lacZ and loxP-flanked D1R coding region underwent homologous recombination in ES cells; (ii) mice derived from these cells transcribed lacZ instead of Drd1a at the D1R allele (D1R^{β-gal/β-gal} mice); (iii) germline recombination at the FRT sites was achieved by breeding these mice with a flp mouse line [Gt(ROSA)^{26Sortm2(FLP*)Sor}] to produce the D1R^flox/flox mouse, in which the Drd1a gene can be excised in the presence of Cre recombinase. Arrows indicate transcription start sites. pA, Transcription termination site; GT, splice acceptor site; IRES, internal ribosome entry site. B, The lack of D1R immunostaining in the outer plexiform layer of Cx57-Cre^+/− D1R^flox/flox mice. Faint residual signal was indistinguishable from that in the global D1R^−/− mouse and, therefore, was nonspecific. Horizontal cells are visualized by calbindin staining. Scale bar, 5 μm.