Inhibitory zinc-enriched terminals in mouse spinal cord.
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.
Danscher
G
G
Department of Neurobiology, Institute of Anatomy, University of Aarhus, Denmark. gd@neuro.au.dk
Jo
S M
SM
Varea
E
E
Wang
Z
Z
Cole
T B
TB
Schrøder
H D
HD
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D005968:Glutamate Decarboxylase / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009411:Nerve Endings / Q000502:physiology*; D009433:Neural Inhibition / Q000502:physiology*; D020033:Protein Isoforms / Q000378:metabolism; D018036:Selenium Compounds; D013116:Spinal Cord / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D014018:Tissue Distribution; D015032:Zinc / Q000378:metabolism*
D002352:Carrier Proteins; D020033:Protein Isoforms; D018036:Selenium Compounds; C017800:zinc-binding protein; D005968:Glutamate Decarboxylase; D015032:Zinc