Synaptic contacts between glutamic acid decarboxylase-immunoreactive boutons and postsynaptic dorsal column neurones...

Neurones with axons ascending the dorsal columns were retrogradely labelled with horseradish peroxidase in the lumbosacral spinal cords of adult cats. Sections, containing labelled neurones, were processed immunocytochemically using an antibody for glutamic acid decarboxylase, the enzyme responsible for the synthesis of gamma-aminobutyric acid (GABA). Thirteen retrogradely labelled cells were observed to receive an average of five contacts each from immunoreactive structures. Ultrastructural investigation revealed that immunolabelled structures were boutons and that some of them were presynaptic to labelled cells. It is concluded that GABA probably mediates at least some of the postsynaptic inhibitory responses which have been recorded from these neurones.