guanosine-5--o-(3-thiotriphosphate) and Migraine-Disorders

F 11356 (4-[4-[2-(2-aminoethyl)-1H-indol-5-yloxyl]acetyl]piperazinyl-1-yl] ben zonitrile) was designed to take advantage of the superior potency and efficacy characteristics of 5-hydroxytryptamine (5-HT) compared with tryptamine at 5-HT1B/1D receptors. F 11356 has subnanomolar affinity for cloned human and nonhuman 5-HT1B and 5-HT1D receptors, and its affinity for 5-HT1A and other 5-HT receptors, including the 5-ht1F subtype, is 50-fold lower and micromolar, respectively. In C6 cells expressing human 5-HT1B or human 5-HT1D receptors, F 11356 was the most potent compound in inhibiting forskolin-induced cyclic AMP formation (pD2 = 8.9 and 9.6), and in contrast to tryptamine and derivatives, it produced maximal enhancement of [35S]guanosine-5'-O-(3-thio)triphosphate-specific binding equivalent to 5-HT. F 11356 was equipotent to 5-HT (pD2 = 7.1 versus 7.2) and more potent than tryptamine derivatives in contracting rabbit isolated saphenous vein. In isolated guinea pig trigeminal ganglion neurons, F 11356 was more potent (pD2 = 7.3 versus 6.7) and induced greater increases in outward hyperpolarizing Ca2+-dependent K+ current than sumatriptan. In anesthetized pigs, F 11356 elicited highly cranioselective, more potent (from 0.16 microgram/kg i.v.) and greater carotid vasoconstriction than tryptamine derivatives. Decreases in carotid blood flow were observed in conscious dogs from 0.63 mg/kg oral F 11356 in the absence of changes in heart rate or behavior. Oral activity was confirmed when hypothermic responses were elicited in guinea pigs (ED50 = 1.6 mg/kg), suggesting that F 11356 also accesses the brain. F 11356 thus is a selective, high-potency agonist at 5-HT1B/1D receptors, which distinguishes itself from tryptamine and derivatives in exerting high intrinsic activity at these receptors in vascular and neuronal models relevant to migraine.

Topics: Animals; Carotid Arteries; Colforsin; Cyclic AMP; Disease Models, Animal; Dogs; Dose-Response Relationship, Drug; Guanosine 5'-O-(3-Thiotriphosphate); Guinea Pigs; Heart; Hemodynamics; Humans; Hypothermia; In Vitro Techniques; Male; Migraine Disorders; Muscle, Smooth, Vascular; Neurons; Nitriles; Piperazines; Rabbits; Radioligand Assay; Rats; Receptor, Serotonin, 5-HT1B; Receptor, Serotonin, 5-HT1D; Receptors, Serotonin; Saphenous Vein; Swine; Trigeminal Ganglion; Tryptamines

The actions of several serotonergic ligands in use or under development for the treatment of migraine headaches were examined at recombinant human 5-HT1A receptors stably expressed in Chinese Hamster Ovary cells. Affinities (K(i)s) at this site were determined in competition binding experiments with [3H]-8-OH-DPAT ([3H](+/-)8-hydroxy-N,N-dipropylaminotetralin), whilst agonist efficacy was measured by stimulation of [35S]-GTP gamma S (guanylyl-5'-[gamma[35S]thio]-triphosphate) binding. Of the prophylactic antimigraine drugs tested, methysergide and lisuride behaved as efficacious agonists (Emax > or = 90% relative to 5-HT) whereas pitozifen and (-)propranolol acted as a partial agonist (60%) and an antagonist, respectively. This suggests that there is no correlation between agonism at 5-HT1A receptors and prophylactic antimigraine action. In contrast, serotonin, dihydroergotamine, sumatriptan, naratriptan and alniditan, which are effective in acute interruption of migraine attacks, each displayed high efficacy (Emax = 100, 100, 92.6, 79.3, 79.1% respectively) and marked affinity (Ki = 18.7, 0.6, 127, 26.4 and 3.0 nM respectively) at 5-HT1A receptors. EC50 values for agonist stimulation of [35S]-GTP gamma S binding correlated with respective Ki values at 5-HT1A receptors (r = 0.93) and the stimulation of [35S]-GTP gamma S binding by these compounds was antagonised by the selective 5-HT1A antagonist WAY 100,635 (N-{2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl}-N-(2-pyridinyl) cyclo-hexanecarboxamide; 100 nM). These data suggest that agonism at 5-HT1A receptors may be involved in some actions of drugs used in acute antimigraine therapy. In comparison with the above compounds, novel ligands targeted at 5-HT1B/1D receptors, such as GR125,743 (N-[4-methoxy-3-(4-methyl-piperazin-1-yl)phenyl] -3-methyl-4-(4-pyridyl)benzamide) and GR 127,935 (N-[4-methoxy-3-(4-methylpiperazin-1-yl)-phenyl]-2'-methyl-4'-(5-m ethyl-1, 2,4-oxadiazol-3-yl)-biphenyl-4-carboxamide), only weakly activated [35S]-GTP gamma S binding (32.4 and 32.1% efficacy) and displayed moderate affinity at 5-HT1A receptors (Kis 53.1 and 49.8 nM) suggesting that they constitute useful tools to differentiate 5-HT1A and 5-HT1B/1D receptor-mediated actions. In conclusion, the present data indicates that several antimigraine agents exhibit marked 5-HT1A receptor activity and that although this is unlikely to be important for prophylactic action it may be relevant to the ancilliary properties of drugs used for a

Topics: 8-Hydroxy-2-(di-n-propylamino)tetralin; Animals; Benzopyrans; Binding, Competitive; Cell Membrane; Cricetinae; Dihydroergotamine; Guanosine 5'-O-(3-Thiotriphosphate); Guinea Pigs; Humans; In Vitro Techniques; Indoles; Lisuride; Methysergide; Migraine Disorders; Piperazines; Piperidines; Pizotyline; Propranolol; Propylamines; Protein Binding; Pyridines; Pyrimidines; Receptors, Serotonin; Receptors, Serotonin, 5-HT1; Recombinant Proteins; Serotonin; Serotonin Antagonists; Serotonin Receptor Agonists; Sumatriptan; Tryptamines