Although working basically through the same mechanism, there are several 5-HT1 receptor subtypes (denoted A-F), each encoded by a separate gene. Furthermore each subtype has a somewhat different tissue distribution and binding preference for synthetic 5-HT1agonist and antagonistligands.
5-HT1B acts on the CNS, where it induces presynaptic inhibition and behavioural effects. It also has vascular effects, such as pulmonary vasoconstriction.
5-HT1D acts on the CNS, and affects locomotion and anxiety. It also induces vascular vasoconstriction in the brain. Ergotamine works primarily through the 5-HT1B receptor, since the effect through the 5-HT1D receptor is contrary to the mode of action of ergotamine, i.e. vasoconstriction.
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