Aminergic innervation of cerebral veins. Histochemical comparison with extracranial veins

The density and distribution pattern of aminergic nerve fibers in intracranial and extracranial veins were compared by means of catecholamine histofluorescence studies. Extracranial veins (internal jugular, inferior caval, portal, renal, internal iliac, and femoral veins) showed quite a uniform distribution pattern. Large veins (jugular, caval, renal, and iliac veins) revealed a spiral pattern, and small veins presented as a meshwork (femoral vein) or in a longitudinal pattern (a branch of the femoral vein). In contrast, intracranial veins displayed more complex patterns: the dural sinus showed a longitudinal pattern and the internal cerebral vein and the superficial vein of Labbé revealed a meshwork of nerve fibers. The aminergic fibers were denser in cerebral veins (dural sinus and internal cerebral vein) than in extracranial veins. The complex distribution and the density of aminergic fibers in cerebral veins suggest that the aminergic innervation of the circulatory system may be more important in the brain than in the extracranial organs.