| Research Abstract |
Subpopulations of GABAergic neurons in the rat hippocampus and dentate gyrus were defined immunohistochemically based on the coexistence of peptides (CCK, VIP) and <Ca^(++)> -binding protein, parvalbumin (PV), with the specific GABA synthesizing enzyme, glutamatic acid decarboxylase (GAD).
Almost all of the CCK-like immunoreactive (LI) neurons were also GAD immunoreactive, whereas only about 10% of GAD immunoreactive neurons were CCK-LI. The percentages of GAD immunoreactive neurons which were also immunoreactive for CCK were dependent on the laminar area in which they were found: i.e., 15-20% in the stratum radiatum, about 10% in the stratum pyramidal and about 6% in the stratum oriens. Furthermore about 1% of GABAergic neurons were indicated to contain both CCK-LI and VIP-LI materials.
On the other hand, almost all PV immunoreactive neurons were also GAD immunoreactive, whereas only about 20% of GAD immunoreactive neurons also contained PV. The percentages of GAD-LI neurons which were also immunoreactive for PV were dependent on the layer in which they were found: i.e., 40-50% in the stratum pyramidale, 20-30% in the stratum oriens and only 1-4% in the stratum radiatum.
As the immunoreactivities of PV and CCK were not contained in the same neuron, GABAergic neurons in the hippocampus may consist of some separate subpopulations of GABAergic neurons.
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