Autoradiographic localization of receptor sites of 3H-muscimol in the CNS of rats.

Radiolabelled muscimol (3-hydroxy-5-aminomethylisoxazole) a potent gamma-amino-butyric acid (GABA) agonist was continuously perfused throughout intraventriculocisternal system of the rat brain. Then the brain tissue was prepared for autoradiography. GABA receptor sites as indicated by 3H-muscimol binding and autoradiographic silver grains display different patterns of distribution over numerous cerebral and spinal cord structures. The precise cellular localization of 3H-muscimol in rat neostriatum was described and compared with other labelled regions of rat brain. The new subpopulations of local neostriatal medium size neurons labelled by 3H-muscimol was identified. The morphology and distribution of the specific neuron subpopulation is discussed. Autoradiographic approach using synthetic analogues structurally related to GABA represent a new tool for morphological demonstration of GABA receptor sites.