IMMUNO-ELECTRON-MICROSCOPIC STUDIES ON THE GAMMA-AMINOBUTYRIC-ACID AND GLYCINE RECEPTOR IN THE INTERMEDIOLATERAL NUCLEUS OF THE THORACIC SPINAL-CORD OF RATS AND GUINEA-PIGS

Gamma-aminobutyric acid (GABA) and glycine are known as major inhibitory neurotransmitters in the intermediolateral nucleus of the spinal cord. Distribution and density of GABA immunoreactive axon varicosities and glycine receptor immunoreactive dendrites and somata in the intermediolateral nucleus were examined by immuno-electronmicroscopy. GABA immunoreaction was observed in the axon varicosities of axo-dendritic and axo-somatic synapses. Glycine receptor immunoreaction was seen in association with the postsynaptic membrane of dendrites and soma. GABA immunoreactive axon varicosities were larger (1.01 +/- 0.49 x 1.20 +/- 0.38-mu-m) than axon varicosities presynaptic to glycine receptors (0.72 +/- 0.22 x 0.98 +/- 0.33-mu-m). The density of GABA immunoreactive axon varicosities was 3.65/100-mu-m2 and that of glycine receptor immunoreactive synapses was 4.78/100-mu-m2. A subpopulation of GABA immunoreactive axons (42%) made synaptic contact with glycine receptor immunoreactive dendrites or soma, indicating the coexistence of GABA and glycine.