Dopamine receptor subtype immunohistochemistry in rat cerebral vassels

The localization of dopamine (DA) receptor subtypes was investigated in rat pial and intracerebral arteries by immunohistochemistry. A faint DA D1 receptor protein immunoreactivitv unaffected by bilateral superior cervical ganglionectomy (BSCGN) was observed in the tunica media of different sized pial arteries. DA D2 receptor protein immunoreactivity was located in the adventitia-media border and disappeared after BSCGN., No apparent changes in the density and pattern of DA D2 receptor protein immunoreactivity were observed in pial arteries of different size. No DA D3 receptor protein immunoreactivity was observed in pial or intracerebral arteries. An intense DA D4 receptor protein immunoreactivity was observed in the adventitia-media transitional zone of pial arteries. DA D4 receptor protein immunoreactivity was more pronounced in medium and small sized pial arteries than in larger ones and disappeared after BSCGN. DA D5 receptor protein immunoreactivity unaffected by BSCGN was localized in the tunica media of different sized pial arteries without changes depending on the size of the vessels examined. Comparatively, among DA receptor subtypes investigated, the D5 receptor was the most expressed of the D1 -like receptor superfamily, the D4 receptor the most expressed of the D2-like receptor superfamily. No DA receptor protein immunoreactivity was observed in intracerebral vessels, whereas adjacent structures known to express DA D1-D5 receptor protein immunoreactivity showed the expected distribution and pattern of immune reaction. These results indicate that different sized pial arteries but not intracerebral arteries express postjunctional (D1 and D5) and prejunctional (D2 and D4) DA receptors. This may have consequences in the regulation of brain perfusion by dopaminergic drugs .