Inhibitory zinc-enriched terminals in mouse spinal cord

• Published in: Neuroscience 2001-01, Vol.105 (4), p.941-947
• Main Authors: Danscher, G, Jo, S.M, Varea, E, Wang, Z, Cole, T.B, Schrøder, H.D
• Format: Article
• Language: English
• Subjects: Anatomy; Animals; autometallography; Biological and medical sciences; Carrier Proteins - metabolism; Central nervous system; Fundamental and applied biological sciences. Psychology; Glutamate Decarboxylase - metabolism; glutamate decarboxylase immunohistochemistry; Male; Mice; Mice, Inbred BALB C; mouse; Nerve Endings - physiology; Neural Inhibition - physiology; Protein Isoforms - metabolism; Selenium Compounds; spinal cord; Spinal Cord - metabolism; Spinal Cord - physiology; Spinal Cord - ultrastructure; Tissue Distribution; Vertebrates: nervous system and sense organs; Zinc - metabolism; zinc transporter-3 immunohistochemistry; zinc-enriched
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(01)00243-3

The ultrastructural localization of zinc transporter-3, glutamate decarboxylase and zinc ions in zinc-enriched terminals in the mouse spinal cord was studied by zinc transporter-3 and glutamate decarboxylase immunohistochemistry and zinc selenium autometallography, respectively. The distribution of zinc selenium autometallographic silver grains, and zinc transporter-3 and glutamate decarboxylase immunohistochemical puncta in both ventral and dorsal horns as seen in the light microscope corresponded to their presence in the synaptic vesicles of zinc-enriched terminals at ultrastructural levels. The densest populations of zinc-enriched terminals were seen in dorsal horn laminae I, III and IV, whereas the deeper laminae V and VI contained fewer terminals. At ultrastructural levels, zinc-enriched terminals primarily formed symmetrical synapses on perikarya and dendrites. Only relatively few asymmetrical synapses were observed on zinc-enriched terminals. In general, the biggest zinc-enriched terminals contacted neuronal somata and large dendritic elements, while medium-sized and small terminals made contacts on small dendrites. The ventral horn was primarily populated by big and medium-sized zinc-enriched terminals, whereas the dorsal horn was dominated by medium-sized and small zinc-enriched terminals. The presence of boutons with flat synaptic vesicles with zinc ions and symmetric synaptic contacts suggests the presence of inhibitory zinc-enriched terminals in the mammalian spinal cord, and this was confirmed by the finding that zinc ions and glutamate decarboxylase are co-localized in these terminals. The pattern of zinc-enriched boutons in both dorsal and ventral horns is compatible with evidence suggesting that zinc may be involved in both sensory transmission and motor control.