1. Structurally novel histamine H3 receptor antagonists GSK207040 and GSK334429 improve scopolamine-induced memory impairment and capsaicin-induced secondary allodynia in rats.
- Author
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Medhurst AD, Briggs MA, Bruton G, Calver AR, Chessell I, Crook B, Davis JB, Davis RP, Foley AG, Heslop T, Hirst WD, Medhurst SJ, Ociepka S, Ray A, Regan CM, Sargent B, Schogger J, Stean TO, Trail BK, Upton N, White T, Orlek B, and Wilson DM
- Subjects
- Analgesics pharmacokinetics, Analgesics pharmacology, Analgesics therapeutic use, Animals, Avoidance Learning drug effects, Azepines administration & dosage, Azepines pharmacokinetics, Benzazepines pharmacokinetics, Benzazepines pharmacology, Central Nervous System drug effects, Drinking drug effects, Histamine Agonists pharmacokinetics, Histamine Agonists pharmacology, Histamine Antagonists pharmacokinetics, Histamine Antagonists pharmacology, Humans, Male, Memory Disorders chemically induced, Neuralgia chemically induced, Pyrazines pharmacokinetics, Pyrazines pharmacology, Pyridines administration & dosage, Pyridines pharmacokinetics, Rats, Rats, Sprague-Dawley, Azepines therapeutic use, Benzazepines therapeutic use, Capsaicin, Histamine Antagonists therapeutic use, Memory Disorders drug therapy, Neuralgia drug therapy, Pyrazines therapeutic use, Pyridines therapeutic use, Receptors, Histamine H3 metabolism, Scopolamine
- Abstract
GSK207040 (5-[(3-cyclobutyl-2,3,4,5-tetrahydro-1H-3-benzazepin-7-yl)oxy]-N-methyl-2-pyrazinecarboxamide) and GSK334429 (1-(1-methylethyl)-4-({1-[6-(trifluoromethyl)-3-pyridinyl]-4-piperidinyl}carbonyl)hexahydro-1H-1,4-diazepine) are novel and selective non-imidazole histamine H(3) receptor antagonists from distinct chemical series with high affinity for human (pK(i)=9.67+/-0.06 and 9.49+/-0.09, respectively) and rat (pK(i)=9.08+/-0.16 and 9.12+/-0.14, respectively) H(3) receptors expressed in cerebral cortex. At the human recombinant H(3) receptor, GSK207040 and GSK334429 were potent functional antagonists (pA(2)=9.26+/-0.04 and 8.84+/-0.04, respectively versus H(3) agonist-induced changes in cAMP) and exhibited inverse agonist properties (pIC(50)=9.20+/-0.36 and 8.59+/-0.04 versus basal GTPgammaS binding). Following oral administration, GSK207040 and GSK334429 potently inhibited cortical ex vivo [(3)H]-R-alpha-methylhistamine binding (ED(50)=0.03 and 0.35 mg/kg, respectively). Functional antagonism of central H(3) receptors was demonstrated by blockade of R-alpha-methylhistamine-induced dipsogenia in rats (ID(50)=0.02 and 0.11 mg/kg p.o. for GSK207040 and GSK334429, respectively). In more pathophysiologically relevant pharmacodynamic models, GSK207040 (0.1, 0.3, 1 and 3mg/kg p.o.) and GSK334429 (0.3, 1 and 3mg/kg p.o.) significantly reversed amnesia induced by the cholinergic antagonist scopolamine in a passive avoidance paradigm. In addition, GSK207040 (0.1, 0.3 and 1mg/kg p.o.) and GSK334429 (3 and 10mg/kg p.o.) significantly reversed capsaicin-induced reductions in paw withdrawal threshold, suggesting for the first time that blockade of H(3) receptors may be able to reduce tactile allodynia. Novel H(3) receptor antagonists such as GSK207040 and GSK334429 may therefore have therapeutic potential not only in dementia but also in neuropathic pain.
- Published
- 2007
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