Origin of porcine brain natriuretic peptide-like immunoreactive innervation of the middle cerebral artery in the rat.

We recently demonstrated that porcine brain natriuretic peptide-like immunoreactive (pBNPir) fibers innervate parts of the cardiovascular system, including the arteries comprising the circle of Willis. To determine the origin of this innervation, we used the retrograde fluorescent tracer Fast Blue dye combined with pBNP immunocytochemistry. Cells which project to the middle cerebral artery and were also pBNPir were found in the trigeminal, pterygopalatine and superior cervical ganglia bilaterally but not in the geniculate or otic ganglia. The majority of these double-labelled cells were found in the ipsilateral trigeminal (46%) and superior cervical ganglia (34%). A pBNP-like substance may be a natural vasodilator in sympathetic, sensory and to a lesser extent parasympathetic neurons innervating the cerebrovascular system.