AMPA Receptor Positive Modulators Research Articles

Positive and negative AMPA receptor modulators based on tricyclic bispidine derivative: Minor structural change inverts the type of activity

Two new potent AMPA receptor allosteric modulators, 6-(1,3-benzodioxol-5-yl)-1,11-dimethyl-3,6,9-triazatri-cyclo[7.3.1.13,11]tetradecane-4,8,12-trione and -4,8-dione were synthesized from 1,3-benzodioxol-5-amine and the corresponding 3,7-dichloroacetyl-3,7-diazabicyclo[3.3.1]-nonanes. In a wide concentration range (10−12–10−7 m), the 12-oxo derivative acts as a positive modulator causing the potentiation of the kainate-induced AMPA receptor currents with maximum potentiation at 1 nm (62%) while its analogue without a ketone group has significant (up to 40%) negative modulator effect. Their tentative mechanisms of action were analyzed by means of molecular modelling

Investigating Opioid‐induced Respiratory Depression and Analgesia Using Larval Zebrafish

Introduction Opioid drugs produce both analgesia and severe respiratory depression which can be lethal. In 2019, over 50,000 North Americans died of an opioid overdose. Our understanding on how to differentiate between these two effects is limited due to a lack of simple animal models. Therefore, we aim to understand respiratory depression and analgesia by opioids using novel zebrafish models, allowing for drug screening. Using these models, we tested a variety of drugs including serotoninergic agonists, glutamatergic modulators, and calcium channel activators, for their ability to reverse opioid-induced respiratory depression. Methods We have established phenotype-based approaches using in-vivo zebrafish models of respiratory depression and analgesia by fentanyl. To quantify respiratory depression, we measured respiratory activity by quantifying mandible movements in 12-14 day post-fertilization larvae. To quantify analgesia, we measured the escape swimming response to nociceptive stimuli such as formalin or allyl isothiocyanate (AITC) combined with fentanyl to induce analgesia. We then introduced various candidate drugs to measure their effects on respiratory depression and analgesia. Results Respiratory rate was normalized to each fish's baseline (baseline=100%). Zebrafish strains were found to be differentially sensitive to opioids, where Tübingen (TU) fish did not respond to fentanyl (1µM, p=0.4240, n=9) and AB fish showed significant respiratory rate depression (p<0.001, n=11). AB and TU crosses did not show respiratory depression (n=7). In AB zebrafish, a dose-dependent decrease in respiratory rate was observed with 1μM and 3µM fentanyl (p=0.01, n=11 and p<0.001, n=27, respectively). The opioid antagonist naloxone (20µM) and selective antagonist CTAP (4μM) reversed respiratory depression by fentanyl (p<0.001, n=9 and p=0.049, n=11, respectively). Respiratory depression by 1μM fentanyl was reversed by the AMPA receptor positive allosteric modulator CX614 (5μM, p<0.001, n=9) but not the serotoninergic 5-HT4 agonist BIMU8 (10μM, n=21). Calcium channel activators nefiracetam (1µM) and FLP-64176 (1µM) reversed respiratory depression by fentanyl (1µM, p=0.005, n=11 and3µM, p<0.001, n=15, respectively). Formalin (0.075%) and AITC (100µM) significantly increased swimming velocity (p=0.005, n=21 and p<0.001, n=23, respectively), which was reduced by fentanyl (4μM, p<0.001, n=12and 6µM, p=0.004, n=14, respectively). FLP-64176 reversed fentanyl analgesia when administered with formalin (p<0.001, n=10). Discussion: Our models show that respiratory depression and analgesia by opioids can be measured in zebrafish larvae. The strain differences point to a potential genetic protection which we are investigating using quantitative real-time polymerase chain reaction (qPCR). Our novel zebrafish models can be used to investigate the effects of opioids, as well as for drug screening to find ways to treat respiratory depression while preserving analgesia.

Ampakines enhance phrenic nerve output in a ZFN rat model of Pompe Disease

Pompe disease (PD) is caused by mutations in the gene encoding acid-α-glucosidase (GAA), an enzyme that degrades lysosomal glycogen. The resultant glycogen accumulation is associated with neurodegeneration, cardiac deficits, and impaired phrenic motoneuron and diaphragm activation. Cardiorespiratory failure is the leading cause of death in early-onset PD patients. We previously reported that a drug which acts as a positive allosteric modulator of AMPA receptors, ampakine CX717, could stimulate phrenic motor output and increase minute ventilation in a mouse model of Pompe disease (Gaa-/-). We recently created a new rat model of PD that better recapitulates the clinical phenotype of early onset PD, called the Zinc Finger Nuclease (ZFN) KO model. Phrenic nerve recordings were performed on urethane anesthetized ZFN KO rats of both sexes, and age-matched wild type (WT) controls during a baseline normoxic period, followed by a brief exposure to hypoxia (PaO2 ~ 30mmHg) and a maximal respiratory challenge with combined hypoxia-hypercapnia. Recordings were done before and after treatment with ampakine CX717 (15mg/kg) or its vehicle control (2-Hydroxypropyl)-β-cyclodextrin. Our goal was to build upon the prior data from the Gaa-/-mouse, by using the ZFN KO model to test the hypothesis that in addition to stimulating basal or “eupneic” phrenic output, ampakine CX717 could also increase the ability to respond to acute respiratory challenge. We also aimed to determine if the extent of phrenic motor deficits were different between male and female ZFN KO rats. The data confirm that both male and female ZFN KO rats exhibit cardiac irregularities and phrenic motor deficits when compared to WT controls. However, a sex difference was apparent as male ZFN KO rats exhibit greater phrenic motor deficits and blunted responses to gas challenges compared to female ZFN KO rats. Ampakine treatment enhanced phrenic output and improved the ability to respond to respiratory challenge in both sexes of the ZNF rat model of PD. We conclude that 1) sex differences are present in the phrenic motor phenotype of ZFN KO rats, 2) the ability of low dose CX717to stimulate phrenic motor output in PD is reproducible across two species, and 3) low dose CX717 can enhance the ability to respond to respiratory challenge in PD rats These data suggest that ampakines may serve as a viable adjunctive therapy for respiratory insufficiency in PD patients.

Novel bivalent positive allosteric AMPA receptor modulator of bis-amide series

A series of bis-amides of bis(aminoalkyl)benzenes and diaminoalkanes were synthesized. Positive modulation of kainate-induced transmembrane currents was registered on Purkinje neurons for isobutyric acid derivative with 1,4-bis(aminomethyl)benzene linker (40% potentiation at 1 nm). This compound also demonstrated a neuroprotective effect at 0.1 nm in an oxidative stress model in HT-22 cells when applied 24 h before H2O2.

AMPA receptors mediate the pro-cognitive effects of electrical and optogenetic stimulation of the medial prefrontal cortex in antidepressant non-responsive Wistar–Kyoto rats

Background:The chronic mild stress (CMS) procedure is a widely used animal model of depression, and its application in Wistar–Kyoto (WKY) rats has been validated as a model of antidepressant-refractory depression. While not responding to chronic treatment with antidepressant drugs, WKY rats do respond to acute deep brain stimulation (DBS) of the medial prefrontal cortex (mPFC). In antidepressant-responsive strains there is evidence suggesting a role for AMPA subtype of glutamate receptor in the action mechanism of both antidepressants and DBS.Methods:Animals were subjected to CMS for 6 to 8 weeks; sucrose intake was monitored weekly and novel object recognition (NOR) test was conducted following recovery from CMS. Wistars were treated chronically with venlafaxine (VEN), while WKY were treated acutely with either DBS, optogenetic stimulation (OGS) of virally-transduced (AAV5-hSyn-ChR2-EYFP) mPFC or ventral hippocampus, or acute intra-mPFC injection of the AMPA receptor positive allosteric modulator CX-516. The AMPA receptor antagonist NBQX was administered, at identical sites in mPFC, immediately following the exposure trial in the NOR.Results:Sucrose intake and NOR were suppressed by CMS, and restored by VEN in Wistars and by DBS, OGS, or CX-516 in WKY. However, OGS of the ventral hippocampal afferents to mPFC was ineffective. A low dose of NBQX selectively blocked the procognitive effect of VEN, DBS and OGS.Conclusions:These results suggest that activation of AMPA receptors in the mPFC represents a common pathway for the antidepressant effects of both conventional (VEN) and novel (DBS, OGS) antidepressant modalities, in both antidepressant responsive (Wistar) and antidepressant-resistant (WKY) rats.

Characterization of a New Positive Allosteric Modulator of AMPA Receptors - PAM-43: Specific Binding of the Ligand and its Ability to Potentiate AMPAR Currents.

Currently, the most dynamic areas in the glutamate receptor system neurobiology are the identification and development of positive allosteric modulators (PAMs) of glutamate ionotropic receptors. PAM-based drugs are of great interest as promising candidates for the treatment of neurological diseases, such as epilepsy, Alzheimer's disease, schizophrenia, etc. Understanding the molecular mechanisms underlying the biological action of natural and synthetic PAMs is a key point for modifying the original chemical compounds as well as for new drug design. We are trying to elaborate a system of molecular functional screening of ionotropic glutamate receptor probable PAMs. The system will be based on the radioligand - receptor method of analysis and will allow rapid quantification of new AMPAR probable PAMs molecular activity. We plan to use a tritiumlabeled analogue of recently elaborated ionotropic GluR probable PAM ([3H]PAM-43) as the main radioligand. Here, we characterized the specific binding of the ligand and its ability to potentiate ionotropic GluR currents. The existence of at least two different sites of [3H]PAM-43 specific binding has been shown. One of the above sites is glutamate-dependent and is characterized by higher affinity. "Patchclamp" technique showed the ability of PAM-43 to potentiate ionotropic GluR currents in rat cerebellar Purkinje neurons in a concentration-dependent manner. The possibility of using PAM-43 as a model compound to study different allosteric effects of potential regulatory drugs (AMPAR allosteric regulators) was shown. [3H]PAM-43 based screening system will allow rapid selection of new AMPAR probable PAM structures and quantification of their molecular activity.

The Anxiolytic Effect of the Neuropeptide Cycloprolylglycine Is Mediated by AMPA and TrkB Receptors.

Previously we have shown that the neuropeptide cycloprolylglycine is an endogenous positive modulator of AMPA receptors and assumed that the pharmacological effects of CPG are associated with the brain neurotrophic factor. In this paper, we have first demonstrated that DNQX, an inhibitor of AMPA receptors, and K252A, an ihibitor of Trk receptors, prevented the anxiolytic effect of CPG, which confirms the formulated hypothesis.

Impact of Ampakine CX‐717 on Diaphragm EMG Activity and Breathing in Non‐anesthetized Freely Behaving Rats

Glutamatergic neurotransmission is partly mediated by ionotropic AMPA receptors, and these receptors play an important role in the neural control of breathing. Ampakines are positive allosteric modulators of AMPA receptors. These drugs can stimulate breathing during hypo‐ventilated states, such as following an opioid overdose. Our laboratory has recently shown that acute exposure to an ampakine, CX717 (15 mg/kg), can acutely stimulate neural drive to the diaphragm in anesthetized but otherwise healthy rats. The goal of the current work is to evaluate the impact of ampakine on diaphragm muscle activation in freely moving non‐anesthetized rats. Ventilation and metabolic rate (VCO2) were measured using whole body plethysmography and diaphragm EMG was assessed using intramuscular electrodes. Spinally intact rats (n=2) were given a single intravenous bolus of CX717 at four months after implantation of diaphragm EMG electrodes. Delivering CX717 at 15 mg/kg had no detectable impact on VCO2, inspiratory tidal volume or diaphragm EMG burst amplitude. In addition, at 30 minutes following IV ampakine, both animals showed a robust increase in diaphragm EMG activity, tidal volume, and the ratio of ventilation VCO2 (VE/VCO2) during an acute hypoxic challenge (5 min, 10.5% inspired O2). Qualitatively, we observed a possible sedative effect as shown of lack of movement and exploratory behavior following ampakine exposure. Our preliminary conclusion is that ampakine CX717 at a dose of 15 mg/kg has little impact on breathing in the otherwise healthy rat. Ongoing studies are evaluating impact of the vehicle (2‐hydroxypropyl‐beta‐cyclodextrin) versus ampakine using a cross‐over study design in spinally intact rats and in rats with spinal cord injury.Support or Funding Information5 R01 HL139708 02 (DDF)F31 HL145831‐01 (MDS)

Auxiliary Proteins are the Predominant Determinants of Differential Efficacy of Clinical Candidates Acting as AMPA Receptor Positive Allosteric Modulators.

Positive allosteric modulators (PAMs) of AMPA receptors boost cognitive performance in preclinical and clinical studies. Their therapeutic window is narrow, however, and clinical application will likely only occur if greater discrimination in activity is achieved. Toward that end, we compared the modulatory activity of two PAMs recently considered as clinical candidates, LY451395 (mibampator) and PF-04958242/BIIB104, on recombinant and native AMPA receptors (AMPARs). We found that the principle molecular determinant that shaped modulatory activity of both PAMs on deactivation (recombinant) and decay (synaptic) of AMPARs was the auxiliary protein incorporated into the receptor complexes. AMPARs containing the stargazin/γ2 transmembrane AMPAR regulatory protein (TARP) were slowed to a >10-fold degree by both PAMs as compared with those incorporating γ8 TARP. Neither subunit composition nor flip/flop splice variation had substantive effect. Similarly, stargazin/γ2-containing mossy fiber EPSCs in cerebellar granule neurons were slowed to a ∼5-fold greater degree than EPSCs in hippocampal CA1 pyramidal cell neurons, which express the γ8 TARP. LY451395 exhibited greater efficacy than BIIB104 at both synapses. These studies provide insight into the receptor constituents that determine efficacy of sulfonamide PAMs. We conclude that compounds that discriminate between AMPARs complexed with distinct TARPs, and particularly those with lower stargazin/γ2 efficacy such as BIIB104, could act as viable procognitive therapeutics. SIGNIFICANCE STATEMENT: Positive allosteric modulators (PAMs) of AMPA receptors enhance cognitive function in a variety of preclinical models. A clearer understanding of the critical determinants of PAM activity could yield critical insight into pathways to maximize their therapeutic index. Here we show that auxiliary proteins for AMPARs play a major, but thus far underappreciated, role in shaping recombinant and neuronal AMPAR modulation by two clinical candidate PAMs. These data will inform both clinical outcomes as well as future rational development of new modulators.

Pharmacological characterisation of MDI-222, a novel AMPA receptor positive allosteric modulator with an improved safety profile

There is considerable interest in positive allosteric modulators (PAMs) of the α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) subtype of ionotropic glutamate receptors as therapeutic agents for a range of cognitive and mood disorders. However, the challenge is to increase AMPA receptor (AMPAR) function sufficient to enhance cognitive function but not to the extent that there are mechanism-related pro-convulsant or convulsant side effects. In this present study, we report the preclinical pharmacology data for MDI-222, an AMPAR PAM which enhances cognition but has a much reduced side-effect (i.e. convulsant) liability relative to other molecules of this mechanism. The pharmacological effects of MDI-222 were characterised in in vitro and in vivo preclinical electrophysiology, efficacy (cognition), side-effect (pro-convulsant/convulsant), tolerability and toxicity assays. We demonstrate that MDI-222 is an AMPAR PAM, since it enhanced AMPAR function in vitro at human (hGluA1-4) and rat (rGluA2) homomeric receptors, and potentiated hetero-oligomeric AMPARs in rat neurons. MDI-222 enhanced electrically evoked AMPAR-mediated synaptic transmission in the anaesthetised rat at 10 mg/kg (administered intravenously) and did not significantly lower the seizure threshold in the pro-convulsant maximal electroshock threshold test (MEST) at any dose tested up to a maximum of 30 mg/kg (administered by oral gavage (p.o.)). MDI-222 reversed a delay-induced deficit in novel object recognition (NOR) in rats with a minimum effective dose (MED) of 0.3 mg/kg (p.o.) following acute administration, which was reduced to 0.1 mg/kg following sub-chronic administration, and improved passive avoidance performance in scopolamine-impaired rats with a MED of 10 mg/kg p.o. On the other hand, MDI-222 was not pro-convulsant in the MEST, resulting in a therapeutic window between plasma concentrations that enhanced cognitive performance and those associated with mechanism-related side effects of ⩾1000-fold. Unfortunately, despite the excellent preclinical profile of this compound, further development had to be halted due to non-mechanism-related issues. We conclude that MDI-222 is an AMPAR PAM which enhances cognitive performance in rats and has a significantly improved safety profile in preclinical species.

Hippocampal gamma rhythms during Y-maze navigation in the juvenile rat.

The neurobiology of postnatal hippocampal development in rodents is receiving increased attention as a means to address neurodevelopmental questions and to better understand the neural code(s) for spatial navigation in adulthood. We previously showed that spontaneous alternation (SA) in a Y-maze, which emerges at the end of the third postnatal week, was related to changes in fast glutamatergic synaptic transmission. In adults, oscillations in the hippocampal local field potential (LFP) (i.e., theta, 4-12 Hz; slow gamma, 25-55 Hz; and fast gamma, 65-100 Hz) have been shown to coordinate the activity of spatially tuned cell types in the hippocampus during route planning and execution. Other investigators have shown that theta activity matures during the first month of life. However, relationships between developmental alterations in gamma oscillations and cognitive function have not been investigated in juveniles, and the impact of developmental changes in excitatory synaptic transmission on network activity remains unclear. We implanted rats at postnatal day 14 to record LFPs from the synaptic layer of area CA1 during Y-maze exploration at postnatal Days 18, 19, 23, and 24. The positive allosteric modulator of AMPA receptors, CX614, or vehicle was administered prior to each test. We found that slow gamma peak frequency, but not peak power, remained constant across this age range. Fast gamma event rate increased with increasing age, while peak frequency decreased. AMPA receptor modulation impacted slow and fast gamma differently at different ages. Furthermore, gamma events showed relationships with novelty and movement speed that differed based on gamma sub-band (slow vs. fast). These results support the presence of environmentally-driven gamma oscillations in hippocampal network activity prior to the end of the third postnatal week of development. Differential refinement of slow and fast gamma occurring across the subsequent week supports involvement in the emergence of spatial navigation ability.

The novel element in the mechanism of endogenous regulation of depressive-like states

It was shown previously that cyclo-prolylglycine, an endogenous neuropeptide, is a positive AMPA receptor modulator and is able to increase the content of BDNF in neurons. In the present work it was shown that cyclo-prolylglycine at a dose of 1 mg/kg with subchronic intraperitoneal administration reduces the time of animal immobility to passive control, from 167.6 to 83.6 s on the 12th day of the experiment using the model of learned helplessness in rats. That indicates the presence of antidepressant-like activity. The results of the study allow us to consider that cyclo-prolylglycine is a link in the physiological regulation of a depressive-like state.

New positive allosteric modulator of AMPA-receptors: in vitro and in vivo studies

A new derivative of 3,7-diazabicyclo[3.3.1]nonane was studied in electrophysiological experiments, which showed high activity as a positive allosteric modulator of AMPA receptors of the CNS. In doses of 0.01 mg/kg this compound significantly improved the memory of experimental animals disturbed by maximal electric shock. The results indicate that this compound is a promising candidate for preclinical and clinical studies as a treatment for a number of psycho-neurological diseases.

Novel Positive Allosteric Modulators of AMPA Receptors Based on 3,7-Diazabicyclo[3.3.1]nonane Scaffold.

A series of new positive allosteric modulators (PAMs) of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors based on 3,7-diazabicyclo[3.3.1]nonane scaffold have been designed, synthesized, and analyzed. In electrophysiological patch clamp studies, several compounds have demonstrated a sub-nanomolar potency. Compound 4 in in vivo tests showed anti-amnestic properties in the scopolamine-induced model of amnesia in the step-through passive avoidance or maximal electroshock experiments in rats at 0.01mg/kg showing a significant "dose-response" advantage over memantine. Based on the analysis of the flexible docking results of PAMs, the cyclothiazide-like mechanism of binding mode was suggested as the major site for the interaction with AMPA receptors.

New Positive Allosteric Modulator of AMPA Receptors: in vitro and in vivo Studies.

A new derivative of 3,7-diazabicyclo[3.3.1]nonane, which showed a high activity as a positive allosteric modulator of AMPA receptors of the CNS, was studied in electrophysiological experiments. At doses of 0.01 mg/kg, this compound significantly improved the memory of experimental animals disturbed by maximal electric shock. The results indicate that this compound is a promising candidate for preclinical trials and clinical studies as a drug for treatment of a number of psychoneurological diseases.

A New Component in the Mechanism of Regulation of Endogenous Depressive-Like States.

It was shown previously that cycloprolylglycine, an endogenous neuropeptide, is a positive AMPA receptor modulator and is able to increase the content of BDNF in neurons. In the present study, using the model of learned helplessness in rats, we showed that cycloprolylglycine at a dose of 1 mg/kg at subchronic intraperitoneal administration reduced the time of animal immobility to passive control values (from 167.6 to 83.6 s) on day 12 of the experiment. This indicates the presence of antidepressant-like activity. The results of the study allow us to consider cycloprolylglycine as a component in the physiological regulation of the depression-like state.

Aniracetam does not improve working memory in neurologically healthy pigeons.

Understanding the effects of cognitive enhancing drugs is an important area of research. Much of the research, however, has focused on restoring memory following some sort of disruption to the brain, such as damage or injections of scopolamine. Aniracetam is a positive AMPA-receptor modulator that has shown promise for improving memory under conditions when the brain has been damaged, but its effectiveness in improving memory in neurologically healthy subjects is unclear. The aim of the present study was to examine the effects of aniracetam (100mg/kg and 200 mg/kg) on short-term memory in “neurologically healthy” pigeons. Pigeons were administered aniracetam via either intramuscular injection or orally, either 30 or 60 minutes prior to testing on a delayed matching-to-sample task. Aniracetam had no effect on the pigeons’ memory performance, nor did it affect response latency. These findings add to the growing evidence that, while effective at improving memory function in models of impaired memory, aniracetam has no effect in improving memory in healthy organisms.

Fully Automated Synthesis and Evaluation of [18F]BPAM121: Potential of an AMPA Receptor Positive Allosteric Modulator as PET Radiotracer

Alzheimer's disease (AD) remains a significant burden on society. In the search for new AD drugs, modulators of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) are of particular interest, as loss of synaptic AMPARs has been linked to AD learning and memory deficits. Previously reported fluorine-containing BPAM121, an AMPA positive allosteric modulator (pam) with high activity, low toxicity, and slow metabolism, was considered to be a perfect 18 F-labeled candidate for positron emission tomography (PET) AD diagnostic investigations. For the preclinical use of this compound, an automated synthesis avoiding human radiation exposure was developed. The detailed production of [18 F]BPAM121 in relatively high quantity using a commercial FASTlab synthesizer from GE Healthcare coupled with a full set of quality controls is presented, along with procedures for the synthesis of the tosylated precursor and the fluorinated reference. To evaluate the clinical usefulness of [18 F]BPAM121 as a potential AD diagnostic, some in vivo studies in mice were then realized, alongside blocking and competition studies.

Regioselective Synthesis of Potent 4,5,6,7-Tetrahydroindazole Derivatives via Microwave-assisted Vilsmeier-Haack Reaction and their Antioxidant Activity Evaluation

Background: Tetrahydroindazole, a member of the fused-pyrazole system, is a least studied class of heterocyclic compounds owing to its scarcity in nature. However, a large number of synthetically prepared tetrahydroindazoles are known to show a variety of biological activities such as interleukin- 2 inducible T-Cell kinase inhibitors, AMPA receptor positive allosteric modulators, antitumor, antituberculosis, anti-inflammatory and antimicrobial activities. Vilsmeier-Haack reaction is one of the most important chemical reactions used for formylation of electron rich arenes. Even though Vilsmeier- Haack reaction was studied on a wide variety of hydrazones derived from active methylene compounds, literature lacks the examples of the use of 4-substituted cyclohexanones as a substrate for the synthesis of 4,5,6,7-tetrahydroindazoles. The study of the reaction of Vilsmeier-Haack reagent with hydrazones derived from cyclic keto compounds having active methylene has been considered the interested topic of investigation. In the present study, ethyl cyclohexanone-4-carboxylate was treated with one equivalent of various hydrazines for two hours and the resulted hydrazones were further treated with an OPC-VH reagent (Vilsmeier-Haack reagent isolated from phthaloyl dichloride and N,Ndimethylformamide) afforded 4,5,6,7-tetrahydroindazoles in excellent yields. The synthesized compounds 4a-f and 5a-f were screened for their antioxidant activities using the DPPH radical scavenging assay. The target compounds were synthesized regioselectively using 4+1 approach in excellent yields. A number of experiments using both conventional heating as well as microwave irradiation methods were tried and on comparison, microwave irradiation method was found excellent in terms of easy work up, high chemical yields, shortened reaction times, clean and, no by-products formation. Some of the synthesized compounds showed significant antioxidant activity. The microwave assisted synthesis of 4,5,6,7-tetrahydroindazoles from ethyl cyclohexanone-4-carboxylate has been reported under mild conditions in excellent yield. Easy work up, high chemical yield, shortened reaction times, clean and no by-products formation are the major advantages of this protocol. These advantages may make this method useful for chemists who are interested in developing novel 4,5,6,7-tetrahydroindazole based drugs.

Bivalent AMPA receptor positive allosteric modulators of the bis(pyrimidine) series.

The first example of a novel class of AMPA receptor positive allosteric modulators of the bis(pyrimidine) series having a hydroquinone linker has been obtained and showed a potency to increase kainate-induced currents at subnanomolar concentrations.