Noradrenergic innervation of the substantia innominata: a light and electron microscopic analysis of dopamine beta-hydroxylase immunoreactive elements in the rat.
Noradrenergic input to the rat substantia innominata (SI) was analyzed in this study by immunocytochemical localization of dopamine beta-hydroxylase (DBH), the synthetic enzyme for noradrenaline. DBH immunoreactive (DBH+) axons ramified extensively within the SI and appeared to be contiguous with the DBH+ terminal fields within the bed nucleus of stria terminalis and the amygdaloid complex. DBH+ axons in the SI exhibited many large boutons en passant and boutons terminaux. These DBH+ boutons appeared much larger than those in the cerebral cortex, hippocampus, and thalamus. Electron microscopic analysis revealed that DBH+ boutons formed asymmetrical synapses with mainly dendrites, but also somata and spines of SI neurons. Dendrites which were postsynaptic to DBH+ boutons also formed synapses with many other unlabeled axon terminals. Since previous studies have shown that dendrites of SI cholinergic neurons formed few synapses, the present result suggests that the noradrenergic influence of SI cholinergic neurons may be mediated mainly by polysynaptic pathways.
Chang
H T
HT
Department of Anatomy and Neurobiology, College of Medicine, University of Tennessee, Memphis.
D000344:Afferent Pathways / Q000648:ultrastructure; D000818:Animals; D001479:Basal Ganglia / Q000648:ultrastructure*; D003712:Dendrites / Q000648:ultrastructure; D004299:Dopamine beta-Hydroxylase / Q000276:immunology; D007150:Immunohistochemistry; D008297:Male; D008854:Microscopy, Electron; D009638:Norepinephrine / Q000502:physiology*; D051381:Rats; D013377:Substantia Innominata / Q000201:enzymology / Q000648:ultrastructure*; D013570:Synaptic Membranes / Q000648:ultrastructure
D004299:Dopamine beta-Hydroxylase; D009638:Norepinephrine