APA Dictionary of Psychology

any of a group of adrenergic blocking agents with selective inhibitory activity, derived from ergot alkaloids. Ergot derivatives act on the central nervous system in a complex manner and, in various forms and doses, can both stimulate and depress higher brain centers. A circulatory effect is vasoconstriction. Some of these agents, including ergotamine, are used in the control of migraine headaches, sometimes combined with other drugs (e.g., caffeine). The derivative ergonovine is used as an oxytocic.