Double Labeling Immulloelectron Microscopic Study on the Synaptic Connections between Glutamic Acid Neurons and GABA Neurons in the Hippocampus of Rats

The pathogenesis of epilepsy is a very complicated process, In which neurotransmltters play important roles. The hippocamplls is a frequently attacked site and an ideal model tissue for epilepsy' l]. In general, the seizure results from the imbalance of excitation and inhibition, i. e., increased effect of excltatory neurotransmltters ordecreased effect of inhlbitory neurotransrnlttersL =' ']. However, there was no nlorphologlcal, eel)eclally at the ultrastructural level, evidenceic identify …

Double Labeling Immulloelectron Microscopic Study on the Synaptic Connections between Glutamic Acid Neurons and GABA Neurons in the Hippocampus of Rats

Summary: In order to explore the roles of different neurotransmitters in epileptic pathogenesis, the synaptic connections between glutamic acid (Gin) neurons and GABA neurons in normal rat hippocampus were studied by pre-embedding double labeling immunoelectron microscopy. The GABA immunoreaction was first demonstrated by chromogen DAB, then the Gin immunoreaction was demonstrated by molybdic acid-TAB method. After being stabilized by DAB-cobalt chloride. the sections were processed for electron microscopic embedding. Under electron microscope, there were many Gin immunoreaction-positive neurons in the pyramidal layer of hippocampal CA1 area and some GABA immunoreaction-positive neurons with pyramidal or polygonal perikarya in the pyramidal, polymorphic and radiant layer of CA1 area. There were also symmetric dendro-axonic synapses formed by GABA-positive dendrites and Glu-positive a-cons in the polymorphic layer and symmetric axo-dendritic synapses formed by GABA-positive axons and Glu-positive dendrites in the radiant layer. In addition, there were symmetric autoregulatory axo-dendritic synapses be- tween Gin-positive axons and dendrites and autoregulatory axo-axonic synapses (both symmetric and asymmetric) between GABA-positive axons. Above mentioned results, for the first time, showed that there were complex synaptic regulatory relationships between excitatory Glu neurons and inhibitory GABA neurons in the hippocampal CA1 area, thereby, providing ultrastructural evidence for different neurotransmitters participating in epileptic pathogenesis.