APA Dictionary of Psychology

any pharmacological substance that either partially or completely inhibits the binding of the neurotransmitters norepinephrine or epinephrine to adrenergic receptors and thus blocks or disrupts the action of these neurotransmitters. Such blocking agents are classed according to whether they inhibit binding to alpha- or beta-adrenergic receptors. They include alpha blockers (also called alpha-adrenoreceptor blocking agents), used primarily to widen blood vessels in the treatment of hypertension, and beta blockers (also called beta-adrenoreceptor blocking agents), used to treat hypertension as well but by reducing the rate and force of heart contractions, arrhythmia, tremor, and anxiety-related symptoms. Also called adrenoceptor blocking agent; adrenoreceptor blocking agent.