Antisera to gamma -aminobutyric acid. 3. Demonstration of GABA in Golgi-impregnated neurons and in conventional electron microscopic sections of cat striate cortex

Two methods are described for the immunocytochemical demonstration of immunoreactive gamma -aminobutyric acid (GABA) in the visual cortex of the cat, an area that contains, several types of GABAergic neurons and requires combined methods for their characterization. While immunocytochemistry was used to determine the probable transmitter of the neuron, Golgi-impregnation of the same cell was used to identify its neuronal type. Since aldehyde-osmium fixation was used, further electron microscopic (EM) analysis of the neuron's synaptic connections was possible. The second procedure demonstrated GABA in EM sections of aldehyde-osmium-fixed cortex using protein A-gold as an immunocytochemical marker. Immunoreactivity was found in certain neurons, dendrites, axons, and boutons forming type II synaptic contacts that from previous studies have been thought to be GABAergic.