Western blots of D1a dopamine receptor. Homogenate of snap-frozen retinas, and protein standards, separated by SDS-PAGE and transferred to nitrocellulose membranes. A, D, Molecular weight (MW) standard proteins, with MW of each indicated in kD by superimposed number. B, Retina proteins run alongside standard proteins in A, and probed with anti-D1a-receptor antibody. A well-focused protein band is seen at migration distance corresponding to an estimated MW of 54 kD. No other proteins are stained over the MW range shown (20–100 kD). C, E, In a different experiment, retina proteins run alongside standard proteins in D. Lane C probed with anti-D1a-receptor antibody that had been pre-incubated overnight with immunogen. Probing of lane E with anti-D1a-receptor antibody shows a well-focused protein band in E at an estimated MW of 54 kD. A faint band is also seen within the MW range reported for glycosylated D1a receptors (here between 55 and 60 kD). Staining of both bands (dark and faint) was blocked completely by immunogen (C).