title: Xanomeline modulation of the blood oxygenation level-dependent signal in awake rats: development of pharmacological magnetic resonance imaging as a translatable pharmacodynamic biomarker for central activity and dose selection.
abstract: In vivo translational imaging techniques, such as positron emission tomography and single-photon emission-computed tomography, are the only ways to adequately determine that a drug engages its target. Unfortunately, there are far more experimental mechanisms being tested in the clinic than there are radioligands, impeding the use of this risk-mitigating approach in modern drug discovery and development. Pharmacological magnetic resonance imaging (phMRI) offers an approach for developing new biomarkers with the potential to determine central activity and dose selection in animals and humans. Using phMRI, we characterized the effects of xanomeline on ketamine-induced activation on blood oxygen level-dependent (BOLD) signal. In the present studies, xanomeline alone dose-dependently increased the BOLD signal across several regions of interest, including association and motor and sensory cortical regions. It is noteworthy that xanomeline dose-dependently attenuated ketamine-induced brain activation patterns, effects that were antagonized by atropine. In conclusion, the muscarinic 1/4-preferring receptor agonist xanomeline suppressed the effects of the N-methyl-D-aspartate channel blocker ketamine in a number of brain regions, including the association cortex, motor cortex, and primary sensory cortices. The region-specific brain activation observed in this ketamine challenge phMRI study may provide a method of confirming central activity and dose selection for novel antipsychotic drugs in early clinical trials for schizophrenia, if the data obtained in animals can be recapitulated in humans.
authors.affiliation: Translational Sciences, Advanced Technology, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Baker
authors.forename: Chih-Liang
authors.initials: CL
authors.lastname: Chin
authors.forename: Ana M
authors.initials: AM
authors.lastname: Basso
authors.forename: Gerard B
authors.initials: GB
authors.lastname: Fox
authors.forename: Gerard J
authors.initials: GJ
authors.lastname: Marek
authors.forename: Mark
authors.initials: M
authors.lastname: Day
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D056004:Molecular Dynamics Simulation; D010101:Oxygen Consumption / Q000187:drug effects / Q000502:physiology*; D011725:Pyridines / Q000378:metabolism* / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013830:Thiadiazoles / Q000378:metabolism* / Q000494:pharmacology*; D014851:Wakefulness / Q000187:drug effects / Q000502:physiology
chemical_list: D015415:Biomarkers; D011725:Pyridines; D013830:Thiadiazoles; C075257:xanomeline