A potential imaging agent for the GABAA receptor: 4-t-butyl-1-(4-[123I]iodophenyl)-2,6,7-trioxabicyclo-[2.2.2]octane.
Based upon the known high toxicity and high antagonist activity of t-butylorthobenzoates towards the GABA receptor complex, 4-t-butyl-1-(4-iodophenyl)-2,6,7-trioxabicyclo[2.2.2]octane 5 and its radioiodo analogues ([123I]-5 and [131I]-5 were prepared as potential markers for the gated chloride channel of GABAA receptors. Mice showed rapid clearance of [131I]-5 from all organs including the brain. The radioactivity was found to proceed into the urine in spite of the high lipophilicity of 5, the high binding affinity of 5 for plasma protein and the apparent chemical stability of 5 in plasma.