sumatriptan, Imitrex
Differential effects of migraine drugs on cerebral blood flow autoregulation.

Vraamark T, Waldemar G, Paulson OB.

Neuroscience Center, Rigshospitalet, Copenhagen, Denmark.

The effect of the migraine drugs ergotamine and sumatriptan on the cerebral blood flow (CBF) autoregulation was studied in halothane/nitrous oxide-anesthetized normotensive Wistar Kyoto rats. Ergotamine, an ergot alkaloid affecting 5HT, norepinephrine, and dopamine receptors, was administered intravenously as a single dose of 25 microg/kg. Sumatriptan, a selective 5HT1-like receptor agonist, was administered by intravenous infusion of 300 microg/kg/h. CBF was measured with the intracarotid 133Xe-injection method. The blood pressure limits of CBF autoregulation were determined by computerized least sum of square analysis. CBF autoregulation was preserved after both ergotamine and sumatriptan. Ergotamine shifted the lower blood pressure limit of CBF autoregulation towards higher blood pressures from 60 +/- 3 mmHg to 82 +/- 4 mmHg (p<0.01), but did not significantly affect the upper blood pressure limit of CBF autoregulation. Sumatriptan had no significant effects on the blood pressure limits of CBF autoregulation.

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sumatriptan, Imitrex
Effects of sumatriptan on coronary flow and left ventricular function in the isolated perfused guinea pig heart.

Le Grand B, Vie B, John GW.

Centre de Recherche Pierre Fabre, Division of Cardiovascular Diseases, Castres, France.

The effects of the 5-HT1B/D receptor agonist, sumatriptan, on coronary flow (CF) and left ventricular function in the isolated perfused guinea pig heart were investigated in the presence and absence of coronary endothelial dysfunction induced by nitric oxide (NO) synthase inhibition with Nomega-nitro-L-arginine methyl ester (L-NAME; 10 microM). Hearts were perfused under constant pressure (80 cm H2O) with oxygenated (95% O2/5% CO2) Krebs bicarbonate buffer (pH 7.4) and were driven at 4 Hz. In the absence of L-NAME (n=37), sumatriptan (0.1-32 microM) failed statistically significantly to affect left ventricular developed pressure (LVDP; maximal change, -8.1+/-1.8%; NS vs. vehicle), left ventricular end-diastolic pressure (LVEDP; +10.4+/-9.8%, NS), or CF (-12.2+/-1.4%; NS compared with vehicle). L-NAME per se significantly reduced coronary flow (CF; -26.3+/-2.9%; p < 0.001), thereby increasing coronary vascular tone, and decreased LVDP (-17.1+/-1.8%; p < 0.01). In hearts perfused with L-NAME (10 microM; n=61), sumatriptan (0.1-32 microM) still failed significantly to affect CF (maximal change, 0.2+/-5.7%, NS) but concentration-dependently increased LVEDP [maximal increase, 89.0+/-30.3%; p < 0.05; geometric mean EC50 3.6 (2.9-5.7) microM], which was not prevented by the 5-HT1B/D receptor antagonist, GR 127935 (0.1 microM; maximal increase, 51.8+/-11.1%; n=48, NS compared with sumatriptan alone). In conclusion, sumatriptan failed significantly to affect CF even in the presence of endothelial dysfunction. LV function similarly remained unaffected in normal hearts, but sumatriptan produced diastolic contracture in the presence of coronary endothelial dysfunction by a mechanism apparently not involving 5-HT1B/D receptors. Collectively the data indicate that 5-HT1B/D receptor expression or effector coupling or both are absent or low in the guinea pig heart, because no detectable functional responses were observed.

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sumatriptan, Imitrex
[Interaction between sumatriptan and selective serotonin uptake inhibitors]

[Article in Norwegian]

Pomp E.

Regionalt Legemiddelinformasjonssenter, Haukeland sykehusapotek, Bergen.

Migraine is common among patients who suffer from depression, and this category of patients often needs drug treatment for both diseases. A pharmacist consulted the Regional Drug Information Centre in the western part of Norway (RELIS 3) about the combined use of sumatriptan and fluoxetine, as the product information on sumatriptan warns of a possible interaction between these drugs. This possibility was evaluated by the Drug Information Centre, and it was concluded that the combination of sumatriptan and a selective serotonin reuptake inhibitor is not contraindicated. This conclusion was based on both theoretical and clinical considerations.

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sumatriptan, Imitrex
Na(+)-dependent metabolic coupling upon 5-HT1B receptor activation by sumatriptan and related agonists.

Pauwels PJ.

Centre de Recherche Pierre Fabre, Department of Cellular and Molecular Biology, Castres, France. crpfl starway.tm.fr.pauwels

The efficacy of the antimigraine compound sumatriptan in migraine relief has been attributed to its interaction with 5-HT1B receptors in cerebral blood vessels causing cranial vasoconstriction, and/or on nerve endings of the trigeminovascular system in the dura mater inhibiting the inflammatory process by decreasing neuropeptide release. Otherwise, the metabolic effects following 5-HT1B receptor activation are largely unknown. In CHO-K1 cells expressing recombinant h5-HT1B receptors, activation of these receptors by sumatriptan and related agonists enhanced their metabolic rate by 34.9%, but not in wild-type cells. Treatment with pertussis toxin (100 ng/ml), addition of the 5-HT1B receptor antagonist GR127935 (30 nM), attenuation or substitution of the extracellular glucose supply, prevented the sumatriptan-mediated enhancement of the metabolic rate. This metabolic enhancement was also blocked by washout of extracellular Na+, independent of the blockade of the Na+/H+ antiporter by ethylisopropylamiloride. The Na(+)-dependent metabolic enhancement by sumatriptan suggests activated 5-HT1B receptors pilot cellular energy demand. This metabolic feature may contribute to the mode of action of 5-HT1B agonists in migraine relief.

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sumatriptan, Imitrex
Comparison of the vasoconstrictor effects of rizatriptan and sumatriptan in human isolated cranial arteries: immunohistological demonstration of the involvement of 5-HT1B-receptors.

Longmore J, Razzaque Z, Shaw D, Davenport AP, Maguire J, Pickard JD, Schofield WN, Hill RG.

Merck Sharp & Dohme Research Laboratories, Neuroscience Research Centre, Eastwick Road, Harlow, Essex, UK.

AIMS: We compared the vasoconstrictor effects of 5-HT with those of the selective 5-HT1B/1D-receptor agonists sumatriptan and rizatriptan in human isolated cranial (middle meningeal) arteries. In addition selective 5-HT1B- or 5-HT1D-receptor antibodies were used in combination with semiquantitative immunohistochemical techniques to compare the levels of expression of these receptors in human middle meningeal and coronary arteries. METHODS: Middle meningeal and coronary arteries were obtained (with consent) from either neurosurgical patients or donor hearts, respectively. Segments of middle meningeal artery were mounted in organ baths for isometric recording and cumulative concentration-effect curves to 5-HT, rizatriptan and sumatriptan were obtained. Frozen fresh sections of middle meningeal and coronary arteries were subjected to standard immunohistochemical techniques using specific 5-HT1B- or 5-HT1D-receptor primary antibodies and a radiolabelled secondary antibody. Data were subjected to analysis of variance (ANOVA) and nonlinear regression analysis. RESULTS: 5-HT, rizatriptan and sumatriptan were potent vasoconstrictors in human isolated middle meningeal artery (EC50 values=32, 90 and 71 nM, respectively). A significantly higher level of 5-HT1B-receptor immunoreactivity was detected in middle meningeal artery compared with coronary artery (ANOVA, F=7.95, DF=1,4, P<0.05). CONCLUSIONS: Rizatriptan and sumatriptan act selectively to cause vasoconstriction in human isolated middle meningeal artery and are 10-fold more potent than in human coronary artery. The higher level of expression of 5-HT1B-receptors in middle meningeal compared with coronary artery provides a pharmacological basis for the craniovascular selectively of both rizatriptan and sumatriptan.

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sumatriptan, Imitrex
Effects of the novel antimigraine agent, frovatriptan, on coronary and cardiac function in dogs.

Parsons AA, Valocik R, Koster P, Raval P, Gagnon R, Tilford N, Feuerstein G.

Neurosciences Research, SmithKline Beecham Pharmaceuticals, Harlow, Essex, England.

The effects of frovatriptan (VML 251/SB-209509) on coronary artery function were investigated in isolated coronary arteries from beagle dogs. Low concentrations of frovatriptan produced contraction with -logEC50 7.55 +/- 0.08 (n = 11). The maximal observed contraction attained was 56 +/- 7% of the control 5-hydroxytryptamine (5-HT; 10 microM) response. At high concentrations of frovatriptan (>6 microM), reversal of sumatriptan (10 microM)-induced contractions was noted. In arteries precontracted with the thromboxane mimetic, U46619, frovatriptan produced a bell-shaped concentration-response relation with a maximal response at 600 nM. Concentrations of frovatriptan >2 microM produced marked reversal of tone, with full relaxation of precontracted tissues at 200 microM. In anesthetized, open-chest mongrel dogs, intravenous (n = 5) or intracoronary (n = 5) artery administration of frovatriptan (0.0001-1 mg/kg) had no consistent effect on left ventricular end-diastolic pressure, left end-systolic pressure, cardiac contractility, aortic blood flow, systemic peripheral resistance, coronary blood flow, coronary vascular resistance, mean arterial blood pressure, or heart rate when compared with vehicle (n = 3). Intravenous sumatriptan produced minor effects on blood pressure and heart rate. Intracoronary artery administration of sumatriptan (0.0003 mg/kg) produced an increase in systemic peripheral resistance to 120.5 +/- 8.2% compared with vehicle (97.8 +/- 5.4%; p < 0.05). This dose of sumatriptan also produced a significant increase in coronary blood flow and decrease in coronary vascular resistance. Intravenous administration of sumatriptan produced a dose-related reduction in left ventricular diastolic pressure with a reduction to 58.3 +/- 8.3% and 41.7 +/- 25% of control values observed at 0.3 and 1 mg/kg, respectively; however, administration of sumatriptan by an intracoronary route had no effect. In a model of myocardial infarction, comparable doses of sumatriptan (1.0 mg/kg) or frovatriptan (0.1 mg/kg), in terms of their effect on carotid vascular resistance, had no significant effect on infarct size. Frovatriptan had no effect on coronary blood flow after reperfusion; however, sumatriptan produced a significant reduction in coronary blood flow for < or =3 h. These studies show that frovatriptan has the capability of relaxing coronary arteries in vitro, has no overall effect on cardiac function at rest with no effect on coronary hemodynamics after myocardial infarction, and has a profile superior to that of sumatriptan.

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sumatriptan, Imitrex
Activation of recombinant h 5-HT1B and h 5-HT1D receptors stably expressed in C6 glioma cells produces increases in Ca2+-dependent K+ current.

Le Grand B, Panissie A, Pauwels PJ, John GW.

Centre de Recherche Pierre Fabre, Castres, France.

The putative coupling between stably expressed recombinant h 5-HT1B or h 5-HT1D receptors and K+ channels which regulate excitability was investigated in C6 glioma cells. Outward K+ currents (IK) were examined in nontransfected C6 glioma cells and in cells expressing cloned h 5-HT1B or h 5-HT1D receptors using the patch-clamp technique in the whole-cell configuration. IK was elicited by a depolarizing step from a holding potential of -60 mV. In C6 glioma cells expressing either recombinant h 5-HT1B or h 5-HT1D receptors, sumatriptan similarly increased IK in a concentration-dependent manner (maximum increase 19.4+/-7.2%, n=8, P<0.05 and 25.1+/-3.9%, n=6, P<0.001, respectively) with EC50 values (geometric mean with 95% confidence intervals in parentheses) of 56.3 nM (7.9-140 nM) and 68.7 nM (16-120 nM), respectively. Sumatriptan failed to elicit increases in IK in non-transfected cells, confirming a specific involvement of the respective membrane h 5-HT1B and h 5-HT1D receptors in transfected C6 cells. In the presence of the mixed 5-HT1B/D receptor antagonist GR 127935 (0.1 microM), sumatriptan (1 microM) failed to significantly increase IK in C6 cells expressing h 5-HT1B receptors (-7.5+/-3.5%, P=NS, n=6), although a higher concentration of GR 127935 (1 microM) was required to significantly inhibit sumatriptan-evoked increases in IK in C6 cells expressing h 5-HT1D receptors (-1.8+/-3.5%, P=NS, n=6), confirming that sumatriptan-evoked responses were indeed mediated by h 5-HT1B and h 5-HT1D receptors, respectively. In C6 cells expressing either cloned h 5-HT1B or h 5-HT1D receptors, sumatriptan-induced increases in IK were prevented by the calcium chelator EGTA (5 mM) when included in the patch pipette (maximum increase 0.57+/-0.6%, n=3, P=NS and -2.8+/-1.6%, n=5, P=NS, respectively). In C6 cells expressing cloned h 5-HT1B receptors, sumatriptan (1 microM) similarly failed to significantly increase IK in the presence of dibutyryl cAMP (10 microM) or when a nominally Ca2+-free medium was included in the patch pipette (-19.4+/-5.1%, n=5 and -5.2+/-4.3%, n=5, respectively, P=NS in each case). In addition, the Ca2+-dependent K+ channel blockers iberiotoxin (0.1 microM) and tetraethylammonium (TEA, 1 mM) abolished sumatriptan-induced increases in IK (-0.5+/-1.0%, n=4 and -3.9+/-3.1%, n=4, respectively, P=NS in each case) in C6 cells expressing h 5-HT1B receptors, confirming the involvement of Ca2+-dependent K+ channels. In C6 cells expressing cloned h 5-HT1B receptors, sumatriptan (1 microM) similarly failed to significantly increase IK after 30-min incubation with thapsigargin (1 microM) or when heparin (2 mg/ml) was included in the patch pipette (1.1+/-0.4%, n=5 and 1.2+/-2.4%, n=5, respectively, P=NS). In conclusion, evidence is provided that both recombinant h 5-HT1B and h 5-HT1D receptors stably transfected in C6 glioma cells are positively coupled to Ca2+-dependent K+ channels, and the outward hyperpolarizing current mediated by these channels is dependent upon IP3 receptor-mediated intracellular Ca2+ release.

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