Beta-adrenergic blockers decrease levels of luteinizing hormone in plasma of orchidectomized rats

The beta-adrenergic antagonists, propranolol and bornaprolol (FM-24), at greater than 2 mg/kg (as [-] form) significantly depressed plasma levels of luteinizing hormone (LH) in orchidectomized rats. This occurred in the absence of consistently significant changes in interpulse intervals or amplitudes of pulsatile LH release. Nadirs of plasma LH decreased significantly even at low blocker doses, with a clear dose dependence for both drugs. The highly significant decrease of plasma LH induced by blocker dosages causing greater than 93% inhibition of beta-adrenergic binding in the anterior pituitary gland was shown to occur without significant changes in binding of specific ligands at pituitary dopamine receptors and hypothalamic alpha 1-adrenergic receptors. The above evidence indicates that beta-blockers may lower LH release in vivo at the level of pituitary beta-adrenergic receptors.