title: Pharmacological properties of SAK3, a novel T-type voltage-gated Ca2+channel enhancer.
abstract: T-type voltage-gated Ca2+channels (T-VGCCs) function in the pathophysiology of epilepsy, pain and sleep. However, their role in cognitive function remains unclear. We previously reported that the cognitive enhancer ST101, which stimulates T-VGCCs in rat cortical slices, was a potential Alzheimer's disease therapeutic. Here, we introduce a more potent T-VGCC enhancer, SAK3 (ethyl 8'-methyl-2',4-dioxo-2-(piperidin-1-yl)-2'H-spiro[cyclopentane-1,3'-imidazo [1,2-a]pyridin]-2-ene-3-carboxylate), and characterize its pharmacological properties in brain. Based on whole cell patch-clamp analysis, SAK3 (0.01-10 nM) significantly enhanced Cav3.1 currents in neuro2A cells ectopically expressing Cav3.1. SAK3 (0.1-10 nM nM) also enhanced Cav3.3 but not Cav3.2 currents in the transfected cells. Notably, Cav3.1 and Cav3.3 T-VGCCs were localized in cholinergic neurve systems in hippocampus and in the medial septum. Indeed, acute oral administration of SAK3 (0.5 mg/kg, p.o.), but not ST101 (0.5 mg/kg, p.o.) significantly enhanced acetylcholine (ACh) release in the hippocampal CA1 region of naïve mice. Moreover, acute SAK3 (0.5 mg/kg, p.o.) administration significantly enhanced hippocampal ACh levels in olfactory-bulbectomized (OBX) mice, rescuing impaired memory-related behaviors. Treatment of OBX mice with the T-VGCC-specific blocker NNC 55-0396 (12.5 mg/kg, i.p.) antagonized both enhanced ACh release and memory improvements elicited by SAK3 administration. We also observed that SAK3-induced ACh releases were significantly blocked in the hippocampus from Cav3.1 knockout (KO) mice. These findings suggest overall that T-VGCCs play a key role in cognition by enhancing hippocampal ACh release and that the cognitive enhancer SAK3 could be a candidate therapeutic in Alzheimer's disease.
authors.affiliation: Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Yabuki
authors.affiliation: Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Matsuo
authors.affiliation: Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
authors.forename: Hisanao
authors.initials: H
authors.lastname: Izumi
authors.affiliation: Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan.
authors.forename: Hidaka
authors.initials: H
authors.lastname: Haga
authors.affiliation: Department of Oral Biology, Graduate School of Dentistry, Tohoku University, Sendai, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Yoshida
authors.affiliation: Department of Oral Biology, Graduate School of Dentistry, Tohoku University, Sendai, Japan.
authors.forename: Minoru
authors.initials: M
authors.lastname: Wakamori
authors.affiliation: Department of Chemistry and Material Engineering, Faculty of Engineering, Shinshu University, Nagano, Japan.
authors.forename: Akikazu
authors.initials: A
authors.lastname: Kakei
authors.affiliation: Department of Cellular Neurobiology, Brain Research Institute, Niigata University, Niigata, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Sakimura
authors.affiliation: Department of Anatomy and Neurobiology, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Takaichi
authors.initials: T
authors.lastname: Fukuda
authors.affiliation: Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan. Electronic address: kfukunaga@m.tohoku.ac.jp.
authors.forename: Kohji
authors.initials: K
authors.lastname: Fukunaga
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001562:Benzimidazoles; D056547:CA1 Region, Hippocampal / Q000378:metabolism / Q000502:physiology; D020747:Calcium Channels, T-Type / Q000187:drug effects* / Q000235:genetics / Q000502:physiology*; D002478:Cells, Cultured; D059329:Cholinergic Neurons / Q000502:physiology; D003521:Cyclopropanes; D004305:Dose-Response Relationship, Drug; D007093:Imidazoles / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007189:Indans / Q000494:pharmacology; D008297:Male; D008568:Memory / Q000187:drug effects; D051379:Mice; D018345:Mice, Knockout; D009281:Naphthalenes; D018697:Nootropic Agents / Q000494:pharmacology; D009830:Olfactory Bulb / Q000601:surgery; D012686:Septal Nuclei / Q000502:physiology; D013141:Spiro Compounds / Q000037:antagonists & inhibitors / Q000494:pharmacology*
chemical_list: D001562:Benzimidazoles; D020747:Calcium Channels, T-Type; D003521:Cyclopropanes; D007093:Imidazoles; D007189:Indans; D009281:Naphthalenes; D018697:Nootropic Agents; C000622095:SAK3 compound; D013141:Spiro Compounds; C511224:spiro(imidazo-(1,2-a)pyridine-3,2-indan)-2(3H)-one; C484287:NNC 55-0396; D000109:Acetylcholine
keywords: Acetylcholine; Cognitive function; Memory; Spiroimidazopyridine; T-type voltage-gated Ca(2+) channel