GAMMA-AMINOBUTYRIC-ACID RECEPTOR DISTRIBUTION IN THE MUSHROOM BODIES OF A FLY (CALLIPHORA-ERYTHROCEPHALA) - A FUNCTIONAL SUBDIVISION OF KENYON CELLS

Antibodies against the Drosophila gamma-aminobutyric acid (GABA) recep tor subunit RDL were used to investigate the significance of inhibitor y inputs to the mushroom bodies in the blowfly (Calliphora erythroceph ala) brain. The pedunculus and the lobes of the mushroom body, which m ainly consist of Kenyon cell fibers, revealed strong immunoreactivity against RDL. Pedunculi, alpha- and beta-lobe show characteristic unsta ined core structures with concentric labeling along the neuropile axis . The gamma-lobes in contrast exhibit a compartmentalized RDL-immunore active pattern. These data suggest an important role of GABAergic inhi bition in the pedunculus and the lobes of insect mushroom bodies. It i s most likely that the RDL-immunoreactivity in the mushroom bodies is closely related to Kenyon cell fibers suggesting that Kenyon cells are an inhomogeneous class of neurons, only part of which receive inhibit ory GABAergic input from extrinsic elements. GABAergic inhibition, the refore, may play a substantial role in the process of learning and mem ory formation in the insect mushroom bodies. (C) 1997 Wiley-Liss, Inc.