Ergot alkaloids pharmacological action

Ergot alkaloids, 517 characteristics, 519 constitution, 525 dihydro-derivatives, 532 hydrolytic products, 526 pharmacological action, 533 relative sympathicolytic activities, 535... 

Katzung PHARMACOLOGY, 9e > Section IV. Drugs with Important Actions on Smooth Muscle > Chapter 16, Histamine, Serotonin, the Ergot Alkaloids > ... 

Sumatriptan and several other "triptans" are selective agonists for 5-HTiD and 5-HTiB receptors. These receptor types are found in cerebral and meningeal vessels and mediate vasoconstriction. They are also found on neurons and probably function as presynaptic inhibitory receptors. These drugs have proved to be very effective in the treatment of acute migraine headache. The mechanism of action is discussed in more detail below under Clinical Pharmacology of Ergot Alkaloids. 

The potent and versatile pharmacological activity of natural ergot alkaloids prompted investigations on the relationship between their chemical structure and physiological action. It also caused the natural alkaloids to be modified chemically and the resulting variations of pharmacological and therapeutic action to be studied. 

All ergot alkaloids which have so far been used therapeutically are lysergic acid derivatives. Representatives of the second main group, the clavine alkaloids, have also been found to be pharmacodynamically active, but as yet, none has been found to exert effects that can be utilized in therapy. The uterotonic and sympatholytic actions are less prominent in their pharmacological spectra of activity but, for example, elymoclavine and agroclavine have a pronounced central excitatory action which is attributed to their stimulation of sympathetic centers (172). 

The multiple pharmacological effects of ergot alkaloids complicate determination of their precise mechanism of action in the acute treatment of migraine. Actions of ergot alkaloids at 5-HTj jj receptors likely mediate their acute antimigraine effects. The ergot derivative methysergide. 

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