Pharmacological Evaluation Of Novel α7 Nicotinic Acetylcholine Receptor Positive Allosteric Modulators And Agonists

Alpha7-nicotinic acetylcholine receptor（α7 nAChR）is a ligand-gated Ca²⁺-permeable homopentameric ion channel that plays an important role in neurotransmitter release and synaptic transmission.Deficit ofα7 function is implicated in cognition and neuropsychiatric disorders.Therefore,pharmacological enhancement ofα7 nAChR function is of great significance for potential therapy of neuropsychiatric diseases characterized with cognitive deficits.At the present,two types of compounds have been identified to enhanceα7 nAChR function:agonist and positive allosteric modulator（PAM）.Agonists ofα7 nAChR can directly stimulate the target receptors,while PAMs modulate the activity ofα7 nAChR by reinforcing the effect of endogenous agonist acetylcholine,resulting in augmented maximal agonist-evoked current or extended decay time of the evoked currents in the continuous presence of agonist,as determined from patch-clamp recordings.On the basis of their macroscopic effects,α7 nAChR PAMs have been classified and distinguished as type I and type II.Type I PAMs mainly enhance agonist-evoked peak currents without delaying desensitization,whereas type II PAMs can delay desensitization.Objective:To confirm the pharmacological activity of the hits identified from the screening in the lab,we evaluated the function of selectedα7 nACh R modulators,including PAMs and agonists,in vitro and in vivo.Methods:In this study,α7 nAChR modulators were evaluated in vitro using electrophysiological techniques such as whole-cell patch clamp and brain slice patch clamp;mouse models such as intraperitoneal injection of NMDA receptor inhibitor MK-801 induced auditory gating deficits,memory impairments and high locomotor activity were used to evaluate the auditory gating,spatial working memory and locomotor activity in vivo.Results:Whole-cell patch clamp recordings of hippocampus neurons indicated that PAM JWX-A0108 potentiated endogenousα7 currents;In brain slice recordings,JWX-A0108resulted in enhanced inhibitory postsynaptic current（IPSC）from CA1 pyramidal neurons and enhanced GABAergic synaptic transmission in hippocampus neurons;In prepulse inhibition test（PPI）,we found that 1)JWX-A0108 reversed auditory gating deficits;2)JWX-A1223 reversed auditory gating deficits,and this effect can be blocked byα7nAChR specific inhibitor MLA;3)Br-IQ17B reversed auditory gating deficits;4)In Y Maze,JWX-A0108 improved spatial working memory impairments;In locomotor activity,JWX-A0108 did not significantly alter the locomotor activity of mice.Conclusions:In the present study,we evaluated a novel type Iα7 nAChR positive allosteric modulator（PAM）6-（2-chloro-6-methyl-phenyl）-2-（3-fluoro-4-methylphenyl）,amino)thiazolo[4,5-d]pyrimidin-7（6H）-one（JWX-A0108）that selectively activatesα7current and reverses MK-801-induced impairment of prepulse inhibition（PPI）of acoustic startle and working memory in mice.In hippocampal slice recordings,JWX-A0108increased both the frequency and amplitude of ACh-evoked GABAergic postsynaptic currents in pyramidal neurons.Our findings indicate thatα7 nAChR type I PAM JWX-A0108 may be beneficial for improvement of cognitive deficits commonly shared by neuropsychiatric disorders such as schizophrenia and Alzheimer’s disease.In addition,we also evaluated the type I PAM compound JWX-A1223 or 3ea（2-Benzylsulfanyl-6-（2-chloro-6-methyl-phenyl）-6H-thiazolo[4,5-d]pyrimidin-7-one）andα7 nAChR selective partial agonist Br-IQ17B（N-[（3R）-1-Azabicyclo[2,2,2]oct-3-yl]-5-bromoindolizine-2-carboxamide）that are capable of reversing MK-801 induced auditory gating deficits.