5-Hydroxytryptamine innervation of vessels in the rat cerebral cortex. Immunohistochemical findings and hydrogen clearance study of rCBF.
The role of the central 5-hydroxytryptamine (5-HT) neuron system in cerebral microcirculation of the rat was examined by immunohistochemical and hydrogen clearance methods. Immunohistochemical studies demonstrated 5-HT-immunoreactive nerve fibers along intraparenchymal blood vessels (arterioles, capillaries, and venules). Ultrastructural observation revealed that 5-HT-immunoreactive terminal boutons (0.3 to 1.0 micron in diameter) made contact with the basement membrane of the capillaries. After an intracerebral injection of 5,7-dihydroxytryptamine (5,7-DHT), a neurotoxin to the 5-HT neuron system, no 5-HT-immunoreactive nerve fibers were found around the injection site with immunohistochemical techniques. With the hydrogen clearance method, the 5,7-DHT-injected cortex showed no significant change in regional cerebral blood flow (rCBF) in the presence of normocapnia, but a significant increase in rCBF with hypercapnia, compared with the untreated cortex. These facts strongly suggest that the central 5-HT neuron system has an important role in carbon dioxide reactivity of the cerebral blood vessels.
D000818:Animals; D001923:Brain Chemistry; D002245:Carbon Dioxide / Q000378:metabolism; D002536:Cerebral Arteries / Q000294:innervation*; D002540:Cerebral Cortex / Q000032:analysis*; D002560:Cerebrovascular Circulation; D007120:Immunochemistry; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000032:analysis*
D002245:Carbon Dioxide; D012701:Serotonin