Porcine carotid artery sections subjected to immunohistochemical staining using antibodies specific for dopamine receptors (DR). D1R (a1 and a2), D2R (panel b) and D3R (c). Two different magnifications of the same section are shown for each (1 = 2X, 2 = 80X). From these representative images, it can be seen that D1 (a), D2 (b), and D3 (c) receptors are all expressed in porcine carotid arteries. D3R are the least abundant, and D2R are the most abundant, which supports our hypothesis that up-regulation of NOS in this vessel is mediated by D2R. Images are representative of 5 vessels (from different pigs) for each receptor staining. Structures: A, adventitia; E, endothelium; I/M, intima/media; L, lumen