Autoradiographic Localization of γ -Aminobutyric Acid (GABA) Receptors in the Rat Cerebellum

[3H]Muscimol was used in the light microscopic autoradiographic localization of gamma-aminobutyric acid (GABA) receptors in the rat cerebellum. The binding of [3H]-muscimol to the slide-mounted tissue sections had all of the characteristics associated with a GABA receptor. It was saturable with appropriate kinetic constants and was blocked only by other GABAergic drugs. Autoradiographic studies revealed a very high density of receptors over the granule cell layer, a low level over the molecular layer, and negligible receptor binding over white matter. This suggested a high localization of GABA receptors to granule cells, which is supported by other neurochemical studies. The autoradiographic procedure used here should be a useful method in further studies of receptors requiring high sensitivity and increased anatomical resolution.