Ultrastructure of descending serotoninergic axonal endings in layers I and II of the dorsal horn.
Serotoninergic axonal endings in layers I and II of the medullary and spinal dorsal horn of the cat were ultrastructurally characterized following uptake of [3H]serotonin. The two most common types were dome-shaped endings which could be distinguished by the size and shape of their agranular synaptic vesicles. The two types of endings were found throughout layers I and II, but were most numerous in layer I. The labeled endings formed both symmetrical and asymmetrical synapses on dendritic shafts and spines, and occasionally a symmetrical synapse on a neuronal soma. Using the technique of anterograde transport of [3H]amino acid, two morphologically identical types of endings were demonstrated as originating from neurons in the caudal raphe nuclei and adjacent reticular formation.
D000344:Afferent Pathways / Q000502:physiology; D000818:Animals; D001369:Axons / Q000378:metabolism / Q000648:ultrastructure*; D002415:Cats; D008526:Medulla Oblongata / Q000502:physiology; D008854:Microscopy, Electron; D012701:Serotonin / Q000378:metabolism*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure
D012701:Serotonin