AbstractConventional film autoradiography was used at the light microscopic level for the localization and quantization of 4‐aminobutyric acid (GABA) receptors in the locust brain (Schistocerca americana). Localization of the receptor site was achieved via binding with the receptor‐ligand probe 3Hmuscimol. Frozen sections were cut and subsequently incubated either in 40 nM 3Hmuscimol or by coincubating sections with 3Hmuscimol and one of the following: GABA (50 μM), a receptor specific agonist muscimol (1 μM) or isoguvacine (1 μM), an uptake inhibitor nipecotic acid (50 μM), or a noncompetitive channel modulator avermectin B1a, (1 μM) or aldrin (50 μM). Through computer image enhancement and densitometric analysis of the optical density of 3Hmuscimol binding sites, the interaction of the above compounds with the putative GABA receptor was determined for various anatomical regions of the locust brain. By comparing the differently treated, but adjacent sections, GABA receptor distribution was quantitated and mapped. Receptor sites were found distributed in the antennal lobes, central body, β‐lobe and β‐lobe of the corpus pedunculatum, protocerebral bridge, and calyx as well as the opt
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