SYNAPTIC CONTACTS BETWEEN GLUTAMIC ACID DECARBOXYLASE-IMMUNOREACTIVE BOUTONS AND POSTSYNAPTIC DORSAL COLUMN NEURONES IN THE SPINAL CORD OF THE CAT

¹ Department of Preclinical Veterinary Sciences, University of Edinburgh, Summerhall, Edinburgh EH9 1QH

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 -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.