GABA-IMMUNOHISTOCHEMISTRY AS A LABEL FOR IDENTIFYING TYPES OF LOCAL INTERNEURONS AND THEIR SYNAPTIC CONTACTS IN THE ANTENNAL LOBES OF THE AMERICAN COCKROACH

Synaptic contacts between GABA-immunoreactive neurons, antennal receptor fibers and non-GABA-immunoreactive neurons in the glomerular neuropil of the antennal lobes have been identified by means of a combination of (i) immunohistochemical labeling and (ii) labeling of afferent fibers of the antenna by experimentally induced degeneration. Characteristic contacts of these neurons are: a) Serially arranged polysynaptic contacts between degenerated antennal fibers, GABA-immunoreactive neurons and non-GABA-immunoreactive neurons. b) Monosynaptic contacts between degenerated antennal fibers and non-GABA-immunoreactive neurons. c) Reciprocal synaptic contacts between immunostained and non-stained neurons and synaptic contacts between individual GABA-immunoreactive neurons. d) Synaptic output contacts of GABA-immunoreactive neurons with degenerated antennal fibers. GABA-immunoreactive neuron profiles in the glomeruli are assigned to multiglomerular local interneurons (Distler 1989a); non-immunolabeled profiles may be assigned to projection neurons and other not yet identified interneurons. © 1990 Springer-Verlag.