[125I]BE 2254, a new high affinity radioligand for alpha 1-adrenoceptors.

[125I]BE 2254 (IBE 2254), a new iodinated radioligand of high specific radioactivity (2175 Ci/mmol) was developed and used to characterize alpha 1-adrenoceptors in rat cerebral cortex membranes. IBE 2254 possessed a high affinity, KD 78 +/- 14 pM with a Bmax of 210 +/- 26 fmol/mg and 90% specific binding at KD value. alpha-Adrenergic antagonists competed for IBE 2254 binding in the following order: prazosin greater than or equal to WB 4101 greater than phentolamine greater than corynanthine greater than yohimbine greater than rauwolscine, a strong indication that IBE 2254 binds to alpha 1-adrenoceptors. IBE 2254 appears to be a very useful tool for studying alpha 1-adrenoceptors.