L-765,314 is a drug which acts as a potent and selective antagonist of the ñ<sub>1</sub>-adrenergic receptor subtype ñ<sub>1B</sub>. It has mainly been used to investigate the role of ñ<sub>1B</sub>-adrenergic receptors in the regulation of blood pressure. The ñ<sub>1B</sub> receptor is also thought to have an important role in the brain; however, L-765,314 does not cross the bloodâÂÂbrain barrier.