Mikeland
Forum Senior
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If the Ergotamine is a partial agonists at alpha adrenoceptor and 5HT2, and 5HT2 has vasodilation as effect. Why ergotamine has vasoconstrictive actions in cerebral vessels?
Does somebody knows why?
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| salmonella
Forum Elite
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bcz partial agonsit act like a competitive antagonist .so if the serotonin act as a vasodilator the partial agonist will contrict it
hope it will help
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| me007
Forum Guru
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it has agonist, partial agonist and antagonist effect.
agonist effect on 5HT2 receptors is vasoconstriction (Katzung)
Another mechanism - like antidepressants may activate 5HT1 on presynaptic trigeminal n ending --> supress excessive firing and inhibit release of vasodilating peptides
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| Mikeland
Forum Senior
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It is logical, however if you or somebody has something else I will apeciated thanks u 
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| salmonella
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thanks me007 u are really a big help
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| Mikeland
Forum Senior
Topics: 24
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How, if the 5HT2 receptor, particulary, has vasodilation effect ( Kaplan pharma pag 238), can be agonist vasoconstrictive?
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| salmonella
Forum Elite
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but I have a question
that kaplan says that serotonin at 5ht2 receptor acts as a vasodilator and bronchial and uterus muscle constrictor ,and I always thought that ergotamine is a partial agonist at this receptor so it will act as antagonist .
If I think acc to kaplan I think I am also not wrong
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| Mikeland
Forum Senior
Topics: 24
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yes, you are right, partial antagonist is the better aswer to my question but not as agonist.
thanks every body for the answers
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