Localization of dopamine D-1 and D-2 receptor mRNAs in the rat systemic and pulmonary vasculatures

The present study was designed to evaluate the expression of dopamine D-1 a nd D-2 receptor mRNAs in systemic and pulmonary vasculatures. Using specifi c antisense riboprobes for dopamine D-1 and D-2 receptor cDNAs, in situ hyb ridization histochemistry was performed in the aorta, common carotid artery , vertebral artery, pulmonary artery, and superior vena cava of the adult m ale Sprague Dawley rat, In the case of the aorta, common carotid artery, an d vertebral artery, dopamine D-1 receptor mRNAs localized mainly in the smo oth muscle cells of the tunica media. However, the signals of dopamine D-2 receptor mRNAs were found in the endothelium and subendothelial layer of tu nica intima, and interstitial cells of tunica adventitia, In the case of th e pulmonary artery, signals of dopamine D-1 receptor mRNAs were detected wi thin the tunica intima, media, and adventitia, Expression of D-2 receptor m RNAs was detected in the walls of small blood vessels within the tunica adv entitia of the pulmonary artery. There were no detectable signals of dopami ne D-1 and D-2 receptor mRNAs in the vein, The uneven distribution of dopam ine D-1 and D-2 receptor mRNAs in the rat systemic vasculatures and pulmona ry artery suggests that dopamine differentially regulates the vasodilation of the systemic and pulmonary arteries through the differential stimulation of dopamine D-1 and D-2 receptor.