3H-muscimol binding sites within the rat choroid plexus: pharmacological characterization and autoradiographic localization.

By using combined radioreceptor binding and autoradiographic techniques, we were able to localize the GABA 'A' receptor agonist 3H-muscimol in the rat choroid plexus. Within sections of rat choroid plexus, 3H-muscimol was bound specifically with a KD of 37 nM and a Bmax of 253 pmol/mg tissue. These values are consistent with the labelling of GABA 'A' receptor sites. The autoradiographic studies demonstrated that 3H-muscimol was attached to the epithelium of the choroid plexus. The blood vessels of the plexus did not exhibit specific labelling. Examination of these data suggests the existence of GABAergic mechanisms which control cerebrospinal fluid production or flow.