Halogenated derivatives of boldine with high selectivity for alpha1A-adrenoceptors in rat cerebral cortex.

The selectivity of 3-nitrosoboldine and different halogenated derivatives of boldine (3-bromoboldine, 3,8-dibromoboldine and 3-chloroboldine) for alpha1-adrenoceptor subtypes was studied by examining [3H]-prazosin competition binding in rat cerebral cortex. In the competition experiments [3H]-prazosin binding was inhibited completely by all the compounds tested. The inhibition curves displayed shallow slopes which could be subdivided into high and low affinity components. The relative order of affinity and selectivity for alpha1A-adrenoceptors was 3-bromoboldine = 3,8-dibromoboldine = 3-chloroboldineboldine3-nitrosoboldine. The competition curves for 3-bromoboldine remained shallow and biph…