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  • 1
    ISSN: 1468-2982
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The venoconstrictive activity of sumatriptan and its interaction with noradrenaline (NA)- and 5-hydroxy-tryptamine (5HT) venoconstriction was studied in vivo in the hand vein of migraineurs. Sumatriptan, injected at increasing doses into the vein, caused local venoconstriction after a 500 mg dose, comparable to that induced by 0.5–1 mg of 5HT. This venoconstriction was completely inhibited by low doses of ketanserin (5 mg). Subcutaneous sumatriptan (6 mg) provoked a minor increase in vein tone, lasting less than 30 min. Non-venoconstrictive doses of sumatriptan (10–100 mg), injected in the hand vein, produced an amplification of NA-venoconstriction but not of 5HT-induced venoconstriction. A similar increased effect was displayed by subcutaneous sumatriptan (6 mg) for at least 1 h. Sumatriptan appears to cause peripheral venoconstriction only at high doses locally applied (in the hand vein), by acting on 5HT2 receptors. Clinical subcutaneous doses (6 mg) do not show significant venoconstrictive effects. The amplifying effect on NA venoconstriction, also caused by 5HT, ergotamine and dihydroergotamine in human cranial arteries, may be important in explaining the therapeutic action of sumatriptan in migraine attacks.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1468-2982
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Substance P-like immunoreactivity (SP-LI) was measured by radioimmunoassay in iris, choroid, and retina obtained from men after death. Although present in different amounts, SP-LI, eluting as authentic SP or SP sulfoxide in the high-performance liquid chromatography system, was found in the three ocular structures. The retina contained higher concentrations of SP-LI than the iris and choroid. The possible functional involvement of iris SP was studied in 22 episodic cluster headache (CH) patients by using the anticholinesterase agent echothiophate iodide (EI), which also induces an atropine-resistant miosis, putatively due to release of SP from trigeminal sensory neurons. In CH patients EI eye drops instilled into both eyes provoked a prolonged miosis with a more marked response in the pupil of the symptomatic eye. It is proposed that the hyperfunction of SP-containing neurons may coexist with the previously documented sympathetic hypofunction in the innervation of the symptomatic pupil of CH.
    Type of Medium: Electronic Resource
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