Influence of catecholamine-derived alkaloids and beta-adrenergic blocking agents on stereospecific binding of 3H-naloxone.

Alkaloids containing a catecholamine moiety, viz., tetrahydroisoquinolines and tetrahydroprotoberberines, and a group of beta-adrenergic blocking agents were examined for their effects on the binding of tritiated naloxone by rat brain homogenate. The stereospecific binding of the opiate antagonist was weakly inhibited by the catecholamine-derived alkaloids. The concentration of alkaloids producing 50% inhibition of binding ranged from 0.06 to 0.37 mM. The inhibitory effects of the beta-adrenergic blocking agents appear to parallel their reported relative local anesthetic actions.