Ultrastructural analysis of tryptophan hydroxylase immunoreactive nerve terminals in the rat cerebral cortex and hippocampus: their associations with local blood vessels

摘要: Physiological evidence has indicated that serotonin (5-hydroxytryptamine) could be a regulator of cerebral blood flow in various regions the brain. In present study, tryptophan hydroxylase immunocytochemistry was used to characterize, both at light and electron microscopic levels, serotonergic nerve terminals primarily their relationships with intraparenchymal microarterioles capillaries rat frontoparietal cortex, entorhinal cortex hippocampus. Irrespective brain area, varicosities were apposed either dendrites or terminals, on average 0.37 micron2 surface area (0.69 micron calculated diameter) 12-22% them engaged synaptic junctions, mostly dendritic elements. Perivascular (defined as immunolabelled located within 3 perimeter around vessel basal lamina) represented 8-11% all immunoreactive counted, determined by microscopy, respectively. hippocampus, proportion perivascular only ultrastructural level corresponded 10% 4%, significantly closer (n = 250, 0.98 +/- 0.05 micron; P < 0.001) vessels than those 116, 1.41 0.08 microns) hippocampus 105, 1.31 microns). Of 26% immediate vicinity (0-0.25 micron) wall, 2.8% directly abutting basement membrane, while 11.6% separated from it thin astrocytic leaflet. This situation contrasts observed where no varicosity ever seen contacting lamina 10-13% being 0.25 vessels. The comparable studied 0.22 micron2; these virtually never contacts adjacent neuronal structures. Our results indicate hydroxylase-immunolabelled are identical previously characterized serotonin-containing varicosities. Furthermore, data show intimate associations between microvessels three examined. However, more frequent and/or much local other regions, might involved neurogenic control flow.