sumatriptan, Imitrex
5-HT1-like receptors mediate 5-hydroxytryptamine-induced contraction of guinea-pig isolated iliac artery.

Sahin-Erdemli I, Hoyer D, Stoll A, Seiler MP, Schoeffter P.

Preclinical Research, Sandoz Pharma AG, Basel, Switzerland.

1. The effects of 5-hydroxytryptamine (5-HT) and of the 5-HT1-like receptor agonists, 5-carboxamidotryptamine (5-CT) and sumatriptan (GR43175) were investigated in isolated ring preparations of guinea-pig common iliac artery. 2. The three agonists induced very weak, if any, contractions of unstimulated preparations, whereas they elicited concentration-dependent contractions in preparations given a moderate tone by a threshold concentration of prostaglandin F2 alpha (PGF2 alpha). 3. Under the latter conditions, Emax values for 5-HT and 5-CT reached about 45% of PGF2 alpha maximal effect, whereas the Emax value of sumatriptan was significantly lower (about 35%). The rank order of potency (mean EC50 value, nM) was 5-CT (6.6) greater than 5-HT (22.9) greater than sumatriptan (155). Pargyline, cocaine or deoxycorticosterone were without significant effect on the contractions induced by 5-HT. 4. The 5-HT3 receptor antagonist, (1 alpha H, 3 alpha,5 alpha H-tropan-3-yl) 1-H-indole-3-carboxylic acid ester (ICS 205-930; 1 microM), had no effect on 5-HT-, 5-CT- and sumatriptan-induced contractions. 5. The 5-HT2 receptor antagonist, ketanserin (1 microM) caused only small rightward shifts (concentration-ratios, about 2) in the concentration-response curves to 5-HT, 5-CT and sumatriptan without significantly depressing the maximum effects. 6. In the presence of ketanserin (1 microM), the non-selective 5-HT receptor antagonist, methiothepin (0.1 microM), shifted the concentration-response curves to 5-HT and 5-CT to the right in a parallel manner and to a similar extent for both agonists (respective mean pKB values, 8.07 and 8.27).(ABSTRACT TRUNCATED AT 250 WORDS)

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1849768&dopt=Abstract sumatriptan Imitrex



sumatriptan, Imitrex
Sumatriptan (GR43175) inhibits cyclic-AMP accumulation in dog isolated saphenous vein.

Sumner MJ, Humphrey PP.

Pharmacology Division, Glaxo Group Research Ltd., Ware, Hertfordshire.

Sumatriptan (GR43175) contracts rings of dog isolated saphenous vein by an action at 5-HT1-like receptors. We have now examined the effects of sumatriptan on prostaglandin E2(PGE2)-stimulated adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation in this tissue. Sumatriptan and 5-hydroxytryptamine (5-HT) produced a concentration-dependent inhibition of PGE2-stimulated cyclic AMP accumulation (EC50 values of 250 nM and 80 nM respectively), responses that were mimicked by 5-carboxamidotryptamine but not by U-46619 or methoxamine. The response to sumatriptan (1 microM) was antagonised by methiothepin (1 microM), but not by metergoline (0.1 microM), spiperone (1 microM) or ondansetron (GR38032, 1 microM). These results suggest that 5-HT1-like receptors which mediate contraction of the dog isolated saphenous vein are negatively coupled to adenylate cyclase in this preparation.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2158369&dopt=Abstract sumatriptan Imitrex



sumatriptan, Imitrex
In vivo effects of sumatriptan (GR 43175) on extracellular levels of 5-HT in the guinea pig.

Sleight AJ, Cervenka A, Peroutka SJ.

Department of Neurology, Stanford University Medical Center, California 94305.

The effect of sumatriptan, a selective 5-HT1D receptor agent, on extracellular levels of 5-HT in the frontal cortex of the guinea pig was measured by intracerebral dialysis. A constant infusion of sumatriptan (10(-8)-10(-7) M) dose-dependently reduced extracellular levels of 5-HT (e.g. 80 +/- 2% decrease from control levels of 5-HT at 10(-7) M). Peripheral administration of sumatriptan (50 micrograms/kg i.p. and 500 micrograms/kg i.p.) had no effect on extracellular levels of 5-HT in the frontal cortex. These data suggest that sumatriptan, when infused into the brain, inhibits the release of 5-HT by stimulating 5-HT autoreceptors and that the putative acute anti-migraine effects of sumatriptan are likely to be mediated by peripheral mechanisms.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2166920&dopt=Abstract sumatriptan Imitrex



sumatriptan, Imitrex
Sumatriptan (GR 43175) interacts selectively with 5-HT1B and 5-HT1D binding sites.

Peroutka SJ, McCarthy BG.

Department of Neurology, Stanford University Medical Center, CA 94305.

The ability of sumatriptan (GR 43175; 3-[2-dimethylamino]ethyl-N-methyl-1H-indole-5 methane sulphonamide) to interact with 13 neurotransmitter receptor sites was determined using radioligand binding techniques. Sumatriptan displayed the highest affinity for 5-HT1D (Ki = 17 nM) and 5-HT1B (Ki = 27 nM) binding sites and was slightly less potent at 5-HT1A binding sites (Ki = 100 nM). By contrast, sumatriptan was essentially inactive (Ki greater than 10,000 nM) at each of the 10 other binding sites analyzed. These data indicate that sumatriptan interacts selectively with 5-HT1B and 5-HT1D sites and suggest that these interactions may be the basis of its apparent efficacy in the acute treatment of migraine.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2545459&dopt=Abstract sumatriptan Imitrex



sumatriptan, Imitrex
Is the unresponsiveness to sumatriptan in cluster headache related to an alteration in the 5-HT receptors?

Stirparo G, Fusco BM, Giacovazzo M, Rinaldi C, Martelletti P.

Institute of Biomedical Technologies, CNR, Rome, Italy.

It is well established that cluster headache shows impaired functions at the neuroimmunomodulatory system level. Defects in the expression of receptors for 5-HT, IL-1 and IL-2 have been found in these patients. Sumatriptan, an agonist activity for 5-HT1D receptor, truncates cluster headache attack in 74% of patients. Flow cytometric analysis of monocytes expressing 5-HT receptor in cluster headache patients showed different trends clearly correlated with the clinical response to sumatriptan. Our findings strongly support the concept that cluster headache patients which are non-responders to sumatriptan could present a block in their 5-HT receptor expression possibly due to specific autoantibodies for this receptor site.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7515379&dopt=Abstract sumatriptan Imitrex



sumatriptan, Imitrex
5-HT1-receptor-mediated vasoconstriction in bovine isolated pulmonary arteries: influences of vascular endothelium and tone.

MacLean MR, Clayton RA, Hillis SW, McIntyre PD, Peacock AJ, Templeton AG.

Institute of Physiology, University of Glasgow, UK.

Vasoconstrictor responses to 5-hydroxytryptamine (5-HT) and the 5-HT1D receptor agonist sumatriptan were studied in isolated bovine pulmonary artery rings. The effects of the antagonists, ketanserin (5-HT2A-receptors) and methiothepin (5-HT1- and 5-HT2A-receptors) on these responses were determined. The influences of vascular tone and the effect of removal of the vascular endothelium and pretreatment with the inhibitor of nitric oxide synthase, N omega-nitro-L-arginine methylester, were also studied. In the absence of tone, in the majority of vessels, sumatriptan did not induce significant contractions. 5-HT-induced responses were concentration-dependent and ketanserin and methiothepin antagonized these in a competitive fashion. Removal of the endothelium or inclusion of L-NAME potentiated responses to sumatriptan. The sensitivity to sumatriptan was increased by L-NAME only in the presence of the endothelium whilst maximum responses to sumatriptan were potentiated in both unrubbed and rubbed vessels. Removal of the endothelium and/or inclusion of L-NAME had no significant effect on responses to 5-HT. U46619-induced tone markedly increased sumatriptan-induced responses which were competitively antagonized by methiothepin but were relatively resistant to ketanserin, verifying activation of a 5-HT1D receptor. Responses to 5-HT were also potentiated and competitively antagonized by ketanserin, and further antagonized by methiothepin. With tone present, lower concentrations of 5-HT were ketanserin-resistant and methiothepin-sensitive, indicating activation of a 5-HT1-like receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7516208&dopt=Abstract sumatriptan Imitrex



sumatriptan, Imitrex
Lack of effect of sumatriptan and UK-14,304 on capsaicin-induced relaxation of guinea-pig isolated basilar artery.

O'Shaughnessy CT, Waldron GJ, Connor HE.

Department of Neuropharmacology, Glaxo Group Research Ltd, Ware, Herts.

1. The objectives of this study were to assess the effects of sensory neuropeptide antagonists and presynaptically acting receptor agonists on capsaicin-induced relaxations of guinea-pig isolated basilar artery (GPBA). 2. Capsaicin, human alpha-calcitonin gene-related peptide (CGRP) and substance P (SP) caused concentration-related relaxations of GPBA which had been pre-contracted with prostaglandin F2 alpha (PGF2 alpha). Responses to capsaicin were not modified by the peptidase inhibitors, phosphoramidon (1 microM) and bestatin (100 microM). 3. The relaxant responses to capsaicin were blocked in a selective manner by ruthenium red (3 microM) and by the CGRP antagonist, CGRP8-37 (1 microM). CGRP8-37 also selectively inhibited the relaxant effects of CGRP. 4. The selective NK1 receptor antagonist, GR82334 (10 microM), inhibited SP-induced relaxations but had little effect on capsaicin-induced relaxations. 5. The 5-HT1 receptor agonist, sumatriptan, produced small contractions of GPBA under conditions of resting tone. In the presence of PGF2 alpha, sumatriptan had no further contractile effect. Sumatriptan (0.3 and 3 microM) did not modify capsaicin-induced relaxations of GPBA. 6. The alpha 2-adrenoceptor agonist, UK-14,304 (0.1 microM), had no effect on basal or PGF2 alpha-induced tone. UK-14,304 did not modify capsaicin-induced relaxations. 7. These results suggest that capsaicin causes relaxation of GPBA via a release of CGRP. This process is amenable to blockade by CGRP8-37 and ruthenium red, but not to modulation by either sumatriptan or UK-14,304.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7679029&dopt=Abstract sumatriptan Imitrex