Clinically effective doses of the triptans correlate well with their affinities for both 5-HT1B and 5-HT1D receptors, which are most likely involved in the mechanism of action of acute antimigraine drugs. 5-HT1B and 5-HT1D receptors are implicated in constriction of intracranial blood vessels. Both 5-HT1B and 5-HT1D receptors serve as presynaptic autoreceptors, modulating neurotransmitter release from neuronal terminals.