Deyi Zhang

Sazetidine-A Is a Potent and Selective Agonist at Native and Recombinant α4β2 Nicotinic Acetylcholine Receptors

Sazetidine-A has been recently proposed to be a “silent desensitizer” of α4β2 nicotinic acetylcholine receptors (nAChRs), implying that it desensitizes α4β2 nAChRs without first activating them. This unusual pharmacological property of sazetidine-A makes it, potentially, an excellent research tool to distinguish between the role of activation and desensitization of α4β2 nAChRs in mediating the central nervous system effects of nicotine itself, as well as those of new nicotinic drugs. We were surprised to find that sazetidine-A potently and efficaciously stimulated nAChR-mediated dopamine release from rat striatal slices, which is mediated by α4β2* and α6β2* subtypes of nAChR. The agonist effects on native striatal nAChRs prompted us to re-examine the effects of sazetidine-A on recombinant α4β2 nAChRs in more detail. We expressed the two alternative stoichiometries of α4β2 nAChR in Xenopus laevis oocytes and investigated the agonist properties of sazetidine-A on both α4(2)β2(3) and α4(3)β2(2) nAChRs. We found that sazetidine-A potently activated both stoichiometries of α4β2 nAChR: it was a full agonist on α4(2)β2(3) nAChRs, whereas it had an efficacy of only 6% on α4(3)β2(2) nAChRs. In contrast to what has been published before, we therefore conclude that sazetidine-A is an agonist of native and recombinant α4β2 nAChRs but shows differential efficacy on α4β2 nAChRs subtypes.

N-(4-((2-(trifluoromethyl)-3-hydroxy-4-(isobutyryl)phenoxy)methyl)benzyl)-1-methyl-1H-imidazole-4-carboxamide (THIIC), a Novel Metabotropic Glutamate 2 Potentiator with Potential Anxiolytic/Antidepressant Properties: In Vivo Profiling Suggests a Link between Behavioral and Central Nervous System Neurochemical Changes

The normalization of excessive glutamatergic neurotransmission through the activation of metabotropic glutamate 2 (mGlu2) receptors may have therapeutic potential in a variety of psychiatric disorders, including anxiety/depression and schizophrenia. Here, we characterize the pharmacological properties of N-(4-((2-(trifluoromethyl)-3-hydroxy-4-(isobutyryl)phenoxy)methyl)benzyl)-1-methyl-1H-imidazole-4-carboxamide (THIIC), a structurally novel, potent, and selective allosteric potentiator of human and rat mGlu2 receptors (EC50 = 23 and 13 nM, respectively). THIIC produced anxiolytic-like efficacy in the rat stress-induced hyperthermia assay and the mouse stress-induced elevation of cerebellar cGMP and marble-burying assays. THIIC also produced robust activity in three assays that detect antidepressant-like activity, including the mouse forced-swim test, the rat differential reinforcement of low rate 72-s assay, and the rat dominant-submissive test, with a maximal response similar to that of imipramine. Effects of THIIC in the forced-swim test and marble burying were deleted in mGlu2 receptor null mice. Analysis of sleep electroencephalogram (EEG) showed that THIIC had a sleep-promoting profile with increased non-rapid eye movement (REM) and decreased REM sleep. THIIC also decreased the dark phase increase in extracellular histamine in the medial prefrontal cortex and decreased levels of the histamine metabolite tele-methylhistamine (t-MeHA) in rat cerebrospinal fluid. Collectively, these results indicate that the novel mGlu2-positive allosteric modulator THIIC has robust activity in models used to predict anxiolytic/antidepressant efficacy, substantiating, at least with this molecule, differentiation in the biological impact of mGlu2 potentiation versus mGlu2/3 orthosteric agonism. In addition, we provide evidence that sleep EEG and CSF t-MeHA might function as viable biomarker approaches to facilitate the translational development of THIIC and other mGlu2 potentiators.

Discovery of selective N-[3-(1-methyl-piperidine-4-carbonyl)-phenyl]-benzamide-based 5-HT1F receptor agonists: Evolution from bicyclic to monocyclic cores

Preclinical experiments and clinical observations suggest the potential effectiveness of selective 5-HT1F receptor agonists in migraine. Identifying compounds with enhanced selectivity is crucial to assess its therapeutic value. Replacement of the indole nucleus in 2 (LY334370) with a monocyclic phenyl ketone moiety generated potent and more selective 5-HT1F receptor agonists. Focused SAR studies around this central phenyl ring demonstrated that the electrostatic and steric interactions of the substituent with both the amide CONH group and the ketone CO group play pivotal roles in affecting the adopted conformation and thus the 5-HT1F receptor selectivity. Computational studies confirmed the observed results and provide a useful tool in the understanding of the conformational requirements for 5-HT1F receptor agonist activity and selectivity. Through this effort, the 2-F-phenyl and N-2-pyridyl series were also identified as potent and selective 5-HT1F receptor agonists.