Catecholaminergic innervation of the spinal dorsal horn: a correlated light and electron microscopic analysis of tyrosine hydroxylase-immunoreactive fibres in the cat.
The ultrastructural organization of presumed catecholamine-containing boutons, in the dorsal horn of the cat lumbosacral spinal cord, was examined in an immunocytochemical study using an antiserum against tyrosine hydroxylase. The study was restricted to the first four laminae of Rexed. Light microscopic inspection revealed numerous, varicose, tyrosine hydroxylase-immunoreactive axons throughout this region of the spinal cord. Within laminae I and II the fibres exhibited a prominent rostrocaudal orientation, while in laminae III and IV they were organized predominantly dorsoventrally. Correlated ultrastructural analysis confirmed that these varicosities were synaptic boutons. Forty-five of these structures were examined through serial sections and they were found to form symmetrical (Gray type II) synaptic junctions with dendrites (95%) and somata (5%). Immunoreactive boutons were not observed to be either presynaptic or postsynaptic to axon terminals. These findings suggest that catecholamines within the spinal dorsal horn act through a postsynaptic action upon dorsal horn neurons.
Doyle
C A
CA
Department of Preclinical Veterinary Sciences, University of Edinburgh, U.K.
Maxwell
D J
DJ
D000344:Afferent Pathways / Q000033:anatomy & histology; D000818:Animals; D001369:Axons / Q000201:enzymology / Q000648:ultrastructure; D015415:Biomarkers; D002415:Cats; D016253:Microscopy, Immunoelectron; D009411:Nerve Endings / Q000737:chemistry; D009412:Nerve Fibers / Q000201:enzymology / Q000648:ultrastructure*; D009475:Neurons, Afferent / Q000201:enzymology; D010146:Pain / Q000503:physiopathology; D013116:Spinal Cord / Q000201:enzymology / Q000648:ultrastructure*; D014446:Tyrosine 3-Monooxygenase / Q000032:analysis*
D015415:Biomarkers; D014446:Tyrosine 3-Monooxygenase