Journal of Neuroscience, Vol 6, 541-552, Copyright © 1986 by Society for Neuroscience
Glutamic acid decarboxylase (GAD) immunocytochemistry of developing rabbit hippocampus
DD Kunkel, AE Hendrickson, JY Wu and PA Schwartzkroin
Immunocytochemical techniques were used to examine the synaptic relations
of inhibitory interneurons in the developing rabbit hippocampus. Glutamic
acid decarboxylase (GAD), the synthesizing enzyme for the inhibitory
neurotransmitter GABA, was found in interneurons of immature (8 d old) as
well as mature (30 d old) tissue. GAD- immunoreactivity was seen in somata,
dendrites, and axon terminals of interneurons at both ages.
Electron-microscopic examination revealed that GAD-positive "terminals" in
immature tissue were often not associated with the usual synaptic
specializations, but were rather in simple apposition to the "postsynaptic"
element. In mature tissue, GAD- positive terminals made symmetric contacts
primarily with pyramidal cell somata, initial segments, and proximal
dendrites. In addition, GAD- positive terminals synapsed onto both
GAD-positive and GAD-negative interneuron profiles.