Ultrastructural organization of the noradrenergic innervation of the superficial gray layer of the hamster's superior colliculus.
Immunocytochemistry with an antibody-directed tyrosine hydroxylase (TH) was combined with electron microscopy and serial-section analysis to examine the synaptic organization of the catecholaminergic projection to the stratum griseum superficiale (SGS) of the hamster's superior colliculus (SC). A total of 250 TH-immunoreactive profiles within SGS were examined. Of these, 114 (45.6%) made synaptic contacts; 81 (71.1%) were axodendritic, and the remainder (33, 28.9%) were axo-axonic. Serial-section analysis was employed to evaluate the presence or absence of synaptic contacts for 26 profiles. Overall, 19 (73.1%) of the profiles followed through serial sections exhibited synaptic contacts. Double staining of single sections with antibodies directed against TH and dopamine-beta-hydroxylase (D beta H) and examination in the light microscope indicated that virtually all TH-positive fibers also contained D beta H. This indicated that the fibers examined at the electron microscopic level were noradrenergic rather than dopaminergic. These results suggest that norepinephrine may have both pre- and postsynaptic actions in the hamster's SC and that at least some of these effects are mediated by conventional synapses.
Arce
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EA
Department of Anatomy, Medical College of Ohio, Toledo 43699-0008.
Bennett-Clarke
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CA
Rhoades
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RW
D000818:Animals; D001369:Axons / Q000201:enzymology / Q000276:immunology / Q000378:metabolism; D006224:Cricetinae; D004299:Dopamine beta-Hydroxylase / Q000276:immunology / Q000378:metabolism; D007122:Immunoelectrophoresis; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D009638:Norepinephrine / Q000378:metabolism / Q000502:physiology*; D013477:Superior Colliculi / Q000201:enzymology / Q000378:metabolism / Q000648:ultrastructure*; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure; D014446:Tyrosine 3-Monooxygenase / Q000276:immunology / Q000378:metabolism
D014446:Tyrosine 3-Monooxygenase; D004299:Dopamine beta-Hydroxylase; D009638:Norepinephrine