In the present study we demonstrated that ketamine, an NMDA antagonist and possible psychotomimetic, increases extracellular histamine (HA) in the rat brain. We then examined the ability of the group ...II mGlu receptor agonist LY379268 to modulate the ketamine evoked increases in HA release in three limbic brain regions. Ketamine (25 mg/kg) increased HA in the medial prefrontal cortex (mPFC), ventral hippocampus (vHipp) and the nucleus accumbens (NAc) shell. LY379268 administered alone was without effect on basal HA efflux in the mPFC or vHipp but modestly decreased HA efflux in the NAc shell. Administration of LY379268 (3 and 10 mg/kg) prior to ketamine significantly attenuated the HA response in the mPFC, vHipp and the NAc shell. The inhibitory effects of LY379268 in the mPFC were mimicked by the systemic administration of the mGlu2 receptor positive allosteric modulator CBiPES (60 mg/kg). Finally, local perfusion experiments revealed that the effects of LY379268 on ketamine evoked HA efflux appear to be mediated by mGlu2 receptors outside the PFC as the intra-mPFC perfusion of LY379268 (100 μM or 300 μM) failed to attenuate ketamine evoked increases in HA efflux. Together, these novel observations reveal an effect of ketamine on histaminergic transmission in limbic brain areas and provide further insight into the possible antipsychotic mechanism of action of mGlu2/3 receptor agonists.
Structure−activity relationships were investigated on the tricyclic dihydropyridine (DHP) KATP openers 9-(3-bromo-4-fluorophenyl)-5,9-dihydro-3H,4H-2,6-dioxa-4-azacyclopentabnaphthalene-1,8-dione (6) ...and 10-(3-bromo-4-fluorophenyl)-9,10-dihydro-1H,8H-2,7-dioxa-9-azaanthracene-4,5-dione (65). Substitution off the core of the DHP, absolute stereochemistry, and aromatic substitution were evaluated for KATP channel activity using Ltk− cells stably transfected with the Kir6.2/SUR2B exon 17− splice variant and in an electrically stimulated pig bladder strip assay. A select group of compounds was evaluated for in vitro inhibition of spontaneous bladder contractions. Several compounds were found to have the unique characteristic of partial efficacy in both the cell-based and electrically stimulated bladder strip assays but full efficacy in inhibiting spontaneous bladder strip contractions. For compound 23b, this profile was mirrored in vivo where it was fully efficacious in inhibiting spontaneous myogenic bladder contractions but only partially able to reduce neurogenically mediated reflex bladder contractions.
The anti-HIV agent (±)-calanolide A (1) has been synthesized in a five-step approach starting with phloroglucinol → 5 → 6 → 11 → 18 → (±)-1, which includes Pechmann reaction, Friedel−Crafts ...acylation, chromenylation with 4,4-dimethoxy-2-methylbutan-2-ol, cyclization, and Luche reduction. Cyclization of chromene 11 to chromanone 18 was achieved by employing either acetaldehyde diethyl acetal or paraldehyde in the presence of trifluoroacetic acid and pyridine or PPTS. Luche reduction of chromanone 18 at lower temperature preferably yielded (±)-1. Reduction of chromone 12, synthesized by Kostanecki−Robinson reaction from chromene 11, failed to afford (±)-1. The synthetic (±)-1 has been chromatographically resolved into its optically active forms, (+)- and (−)-1. The anti-HIV activities for synthetic (±)-1, as well as resultant (+)- and (−)-1, have been determined. Only (+)-1 accounted for anti-HIV activity, which was similar to the data reported for the natural product, and (−)-1 was inactive.
Transmembrane AMPA receptor regulatory proteins (TARPs) are a family of scaffolding proteins that regulate AMPA receptor trafficking and function. TARP γ-8 is one member of this family and is highly ...expressed within the hippocampus relative to the cerebellum. A selective TARP γ-8-dependent AMPA receptor antagonist (TDAA) is an innovative approach to modulate AMPA receptors in specific brain regions to potentially increase the therapeutic index relative to known non-TARP-dependent AMPA antagonists. We describe here, for the first time, the discovery of a noncompetitive AMPA receptor antagonist that is dependent on the presence of TARP γ-8. Three major iteration cycles were employed to improve upon potency, CYP1A2-dependent challenges, and in vivo clearance. An optimized molecule, compound (−)-25 (LY3130481), was fully protective against pentylenetetrazole-induced convulsions in rats without the motor impairment associated with non-TARP-dependent AMPA receptor antagonists. Compound (−)-25 could be utilized to provide proof of concept for antiepileptic efficacy with reduced motor side effects in patients.
In vivo anti-HIV efficacy of (+)-calanolide A has been evaluated in a hollow fiber mouse model. It was demonstrated that the compound was capable of suppressing virus replication in two distinct and ...separate physiologic compartments (ip and sc) following oral or parenteral administration on a once- or twice-daily treatment schedule. A synergistic effect was observed for the combination of (+)-calanolide A and AZT.
In vivo anti-HIV efficacy of (+)-calanolide A has been evaluated in a hollow fiber mouse model. It was demonstrated that the compound was capable of suppressing virus replication in two distinct and separate physiologic compartments (ip and sc) following oral or parenteral administration on a once- or twice-daily treatment schedule. A synergistic effect was observed for the combination of (+)-calanolide A and AZT.
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 (EC(50) = 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.
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Pyridylmethylsulfonamide series were the first reported example of positive allosteric modulators (PAM) of the mGlu2 receptor. The hydroxyacetophenone scaffold is a second series of ...mGlu2 PAMs we have identified. This series of molecules are potent mGlu2 potentiators and possess significant CysLT1 (cysteinyl leukotriene receptor 1) antagonist activity, showing in vivo efficacy in a dural plasma protein extravasation (PPE) model of migraine. In this paper, we describe the dual SAR, pharmacokinetics and preclinical in vivo efficacy data for a tetrazole containing hydroxyacetophenone scaffold.
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Negative modulators of metabotropic glutamate 2 & 3 receptors demonstrate antidepressant-like activity in animal models and hold promise as novel therapeutic agents for the treatment ...of major depressive disorder. Herein we describe our efforts to prepare and optimize a series of conformationally constrained 3,4-disubstituted bicyclo3.1.0hexane glutamic acid analogs as orthosteric (glutamate site) mGlu2/3 receptor antagonists. This work led to the discovery of a highly potent and efficacious tool compound 18 (hmGlu2 IC50 46±14.2nM, hmGlu3 IC50=46.1±36.2nM). Compound 18 showed activity in the mouse forced swim test with a minimal effective dose (MED) of 1mg/kg ip. While in rat EEG studies it exhibited wake promoting effects at 3 and 10mg/kg ip without any significant effects on locomotor activity. Compound 18 thus represents a novel tool molecule for studying the impact of blocking mGlu2/3 receptors both in vitro and in vivo.
The synthesis of (+)-calanolide A (
1), an anti-HIV-1 agent, is described. A TiCl
4-mediated aldol reaction of compound
2 stereoselectively produced the desired
syn diastereomer (±)-
5, which was ...resolved by a lipase-catalyzed acylation reaction. Under Mitsunobu conditions (Ph
3P/DEAD), the
syn aldol product (+)-
5 led to the formation of
trans-2,3-dimethyl chroman-4-one (+)-
3 with 94%
ee, while the
anti aldol product (+)-
6 yielded both
trans and
cis derivatives (+)-
3 and (+)-
4 with 60% and 68%
ee, respectively. Luche reduction on (+)-
3 led to (+)-
1 and (+)-calanolide B in a ratio of 9:1.
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