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Additive effects of a cholinesterase inhibitor and a histamine inverse agonist on scopolamine deficits in humans.

Author(s): Cho W, Maruff P, Connell J, Gargano C, Calder N, Doran S, Fox-Bosetti S, Hassan A, Renger J, Herman G, Lines C, Verma A

Affiliation(s): Merck Sharp & Dohme Corp, Whitehouse Station, NJ, USA, cho.william@gene.com.

Publication date & source: 2011-12, Psychopharmacology (Berl)., 218(3):513-24. Epub 2011 Jun 7.

RATIONALE: Enhancement of histaminergic neurotransmission or histaminergic plus cholinergic neurotransmission may represent novel strategies for improving cognition in Alzheimer's disease. OBJECTIVE: To evaluate the effects of a novel histamine H3 receptor inverse agonist (MK-3134), an acetylcholinesterase inhibitor (donepezil), and their combination in attenuating the cognitive impairment associated with scopolamine. METHODS: Thirty-one subjects were randomized, and 28 completed this double-blind, placebo-controlled, five-period crossover study. Cognition was assessed using the Groton Maze Learning Task (GMLT) as the primary outcome measure. The two primary hypotheses were that donepezil 10 mg and MK-3134 25 mg, respectively, would attenuate scopolamine (0.5 mg)-induced impairment as measured by the GMLT over the first 12 h after scopolamine administration (AUC(1-12) (h)). A secondary hypothesis was that the combination of donepezil and MK-3134 would attenuate scopolamine-induced cognitive impairment to a greater extent than either agent alone as measured by the GMLT AUC(1-12 h). RESULTS: The primary and secondary hypotheses were not met. Upon examining the time course of the scopolamine effects (an exploratory objective), peak effects were generally observed around 2 h after scopolamine administration. Administration of MK-3134 or donepezil improved performance on the GMLT at the 2-h time point, rather than AUC(1-12 h), compared with scopolamine alone. Moreover, it appeared that the combination of MK-3134 and donepezil blunted the scopolamine effect to a greater extent than either drug alone. CONCLUSIONS: Exploratory analyses provide evidence for cognitive improvement through inverse agonism of the H3 histamine receptor and for cooperation between human cholinergic and histaminergic neurotransmitter systems. (ClinicalTrials.gov trial registration number: NCT01181310).

Page last updated: 2011-12-09

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