Development of Novel Tools for Dissection of Central Versus Peripheral Dopamine D2-Like Receptor Signaling in Dysglycemia.

Dopamine (DA) D2-like receptors in both the central nervous system (CNS) and the periphery are key modulators of metabolism. Moreover, disruption of D2-like receptor signaling is implicated in dysglycemia. Yet, the respective metabolic contributions of CNS versus peripheral D2-like receptors, including D2 (D2R) and D3 (D3R) receptors, remain poorly understood.

Development of novel tools for dissection of central versus peripheral dopamine D-like receptor signaling in dysglycemia.

Dopamine (DA) D-like receptors in both the central nervous system (CNS) and the periphery are key modulators of metabolism. Moreover, disruption of D-like receptor signaling is implicated in dysglycemia. Yet, the respective metabolic contributions of CNS versus peripheral D-like receptors including D (D2R) and D (D3R) receptors remain poorly understood.

Pharmacologic Characterization of Substituted Nitazenes at , , and Opioid Receptors Suggests High Potential for Toxicity.

The benzimidazole opioids (substituted nitazenes) are highly potent opiod receptor (MOR) agonists with heroin- or fentanyl-like effects. These compounds have caused hospitalizations and fatal overdoses. We characterized the in vitro pharmacology and structure-activity relationships of 19 nitazenes with substitutions at three positions of the benzimidazole core.

Pharmacologic Activity of Substituted Tryptamines at 5-Hydroxytryptamine (5-HT) Receptor (5-HTR), 5-HTR, 5-HTR, and Serotonin Transporter.

Novel psychoactive substances, including synthetic substituted tryptamines, represent a potential public health threat. Additionally, some substituted tryptamines are being studied under medical guidance as potential treatments of psychiatric disorders. Characterizing the basic pharmacology of substituted tryptamines will aid in understanding differences in potential for harm or therapeutic use.

A highly DR-selective and efficacious partial agonist (S)-ABS01-113 compared to its DR-selective antagonist enantiomer (R)-ABS01-113 as potential treatments for opioid use disorder.

The non-medical use of opioids has become a national crisis in the USA. Developing non-opioid pharmacotherapies for controlling this opioid epidemic is urgent. Dopamine D receptor (DR) antagonists and low efficacy partial agonists have shown promising profiles in animal models of opioid use disorders (OUD).

New dual 5-HT1A and 5-HT7 receptor ligands derived from SYA16263.

We have previously reported that dual 5-HT and 5-HT receptor ligands might find utility as treatment options for various CNS related conditions including cognitive and anxiolytic impairments. We have also more recently reported that SYA16263 has antipsychotic-like properties with an absence of catalepsy in animal models ascribed to its ability to recruit β-arrestin to the D receptor. However, SYA16263 also binds with very high affinity to 5-HTR (Ki = 1.

Affinity, potency, efficacy, selectivity, and molecular modeling of substituted fentanyls at opioid receptors.

Substituted fentanyls are abused and cause rapid fatal overdose. As their pharmacology is not well characterized, we examined in vitro pharmacology and structure-activity relationships of 22 substituted fentanyls with modifications of the fentanyl propyl group, and conducted in silico receptor/ligand modeling. Affinities for mu, kappa, and delta opioid receptors (MOR, KOR, and DOR, respectively) heterologously expressed in mammalian cells were assessed in agonist radioligand binding assays.

Fentanyl but not Morphine Interacts with Nonopioid Recombinant Human Neurotransmitter Receptors and Transporters.

Synthetic opioids, including fentanyl and its analogs, have therapeutic efficacy in analgesia and anesthesia. However, their illicit use in the United States has increased and contributed to the number one cause of death for adults 18-50 years old. Fentanyl and the heroin metabolite morphine induce respiratory depression that can be treated with the opioid receptor (MOR) antagonist naloxone.

Activation of Trace Amine-Associated Receptor 1 Stimulates an Antiapoptotic Signal Cascade via Extracellular Signal-Regulated Kinase 1/2.

Methamphetamine (MA) is highly addictive and neurotoxic, causing cell death in humans and in rodent models. MA, along with many of its analogs, is an agonist at the G protein-coupled trace amine-associated receptor 1 (TAAR1). TAAR1 activation protects against MA-induced degeneration of dopaminergic neurons, suggesting that TAAR1 plays a role in regulating MA-induced neurotoxicity.

Repurposing of a Nucleoside Scaffold from Adenosine Receptor Agonists to Opioid Receptor Antagonists.

While screening off-target effects of rigid ()-methanocarba-adenosine 5'-methylamides as A adenosine receptor (AR) agonists, we discovered μM binding hits at the δ-opioid receptor (DOR) and translocator protein (TSPO). In an effort to increase OR and decrease AR affinity by structure activity analysis of this series, antagonist activity at κ-(K)OR appeared in 5'-esters (ethyl and propyl ), which retained TSPO interaction (μM). 7-Deaza modification of C2-(arylethynyl)-5'-esters but not 4'-truncation enhanced KOR affinity (MRS7299 and , ≈ 40 nM), revealed μ-OR and DOR binding, and reduced AR affinity.

Structure-activity relationships of bath salt components: substituted cathinones and benzofurans at biogenic amine transporters.

Rationale: New psychoactive substances (NPSs), including substituted cathinones and other stimulants, are synthesized, sold on the Internet, and ingested without knowledge of their pharmacological activity and/or toxicity. In vitro pharmacology plays a role in therapeutic drug development, drug-protein in silico interaction modeling, and drug scheduling.

Objectives: The goal of this research was to determine mechanisms of action that may indicate NPS abuse liability.

Neurochemical pharmacology of psychoactive substituted N-benzylphenethylamines: High potency agonists at 5-HT receptors.

The use of new psychoactive substituted 2,5-dimethoxy-N-benzylphenethylamines is associated with abuse and toxicity in the United States and elsewhere and their pharmacology is not well known. This study compares the mechanisms of action of 2-(2,5-dimethoxy-4-methylphenyl)-N-(2-methoxybenzyl)ethanamine (25D-NBOMe), 2-(4-ethyl-2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethanamine (25E-NBOMe), 2-(2,5-dimethoxyphenyl)-N-(2-methoxybenzyl)ethanamine (25H-NBOMe), 2-(((4-iodo-2,5-dimethoxyphenethyl)amino)methyl)phenol (25I-NBOH); and 2-(2,5-dimethoxy-4-nitrophenyl)-N-(2-methoxybenzyl)ethanamine) (25N-NBOMe) with hallucinogens and stimulants. Mammalian cells heterologously expressing 5-HT, 5-HT, 5-HT or 5-HT receptors, or dopamine, serotonin or norepinephrine transporters (DAT, SERT and NET, respectively) were used to assess drug affinities at radioligand binding sites.

Synthesis and Discovery of Arylpiperidinylquinazolines: New Inhibitors of the Vesicular Monoamine Transporter.

Methamphetamine, a human vesicular monoamine transporter 2 (VMAT2) substrate, releases dopamine, serotonin, and norepinephrine from vesicles into the cytosol of presynaptic neurons and induces reverse transport by the monoamine transporters to increase extracellular neurotransmitters. Currently available radioligands for VMAT2 have considerable liabilities: The binding of [H]dihydrotetrabenazine ([H]DHTB) to a site on VMAT2 is not dependent on ATP, and [H]reserpine binds almost irreversibly to VMAT2. Herein we demonstrate that several arylpiperidinylquinazolines (APQs) are potent inhibitors of [H]reserpine binding at recombinant human VMAT2 expressed in HEK-293 cells.

Verification of a genetic locus for methamphetamine intake and the impact of morphine.

A quantitative trait locus (QTL) on proximal chromosome (Chr) 10 accounts for > 50% of the genetic variance in methamphetamine (MA) intake in mice selectively bred for high (MAHDR) and low (MALDR) voluntary MA drinking. The µ-opioid receptor (MOP-r) gene, Oprm1, resides at the proximal end of Chr 10, and buprenorphine reduces MA intake in MAHDR mice. However, this drug has only partial agonist effects at MOP-r.

Scaffold Repurposing of Nucleosides (Adenosine Receptor Agonists): Enhanced Activity at the Human Dopamine and Norepinephrine Sodium Symporters.

We have repurposed (N)-methanocarba adenosine derivatives (A adenosine receptor (AR) agonists) to enhance radioligand binding allosterically at the human dopamine (DA) transporter (DAT) and inhibit DA uptake. We extended the structure-activity relationship of this series with small N-alkyl substitution, 5'-esters, deaza modifications of adenine, and ribose restored in place of methanocarba. C2-(5-Halothien-2-yl)-ethynyl 5'-methyl 9 (MRS7292) and 5'-ethyl 10 (MRS7232) esters enhanced binding at DAT (EC ∼ 35 nM) and at the norepinephrine transporter (NET).

Structure-Activity Relationships of Substituted Cathinones, with Transporter Binding, Uptake, and Release.

Synthetic cathinones are components of "bath salts" and have physical and psychologic side effects, including hypertension, paranoia, and hallucinations. Here, we report interactions of 20 "bath salt" components with human dopamine, serotonin, and norepinephrine transporters [human dopamine transporter (hDAT), human serotonin transporter (hSERT), and human norepinephrine transporter (hNET), respectively] heterologously expressed in human embryonic kidney 293 cells. Transporter inhibitors had nanomolar to micromolar affinities (K values) at radioligand binding sites, with relative affinities of hDAT>hNET>hSERT for α-pyrrolidinopropiophenone (α-PPP), α-pyrrolidinobutiophenone, α-pyrrolidinohexiophenone, 1-phenyl-2-(1-pyrrolidinyl)-1-heptanone, 3,4-methylenedioxy-α-pyrrolidinopropiophenone, 3,4-methylenedioxy-α-pyrrolidinobutiophenone, 4-methyl-α-pyrrolidinopropiophenone, α-pyrrolidinovalerophenone, 4-methoxy-α-pyrrolidinovalerophenone, α-pyrrolidinopentiothiophenone (alpha-PVT), and α-methylaminovalerophenone, and hDAT>hSERT>hNET for methylenedioxypentedrone.

Genetic Polymorphisms Affect Mouse and Human Trace Amine-Associated Receptor 1 Function.

Methamphetamine (MA) and neurotransmitter precursors and metabolites such as tyramine, octopamine, and β-phenethylamine stimulate the G protein-coupled trace amine-associated receptor 1 (TAAR1). TAAR1 has been implicated in human conditions including obesity, schizophrenia, depression, fibromyalgia, migraine, and addiction. Additionally TAAR1 is expressed on lymphocytes and astrocytes involved in inflammation and response to infection.

Rigid Adenine Nucleoside Derivatives as Novel Modulators of the Human Sodium Symporters for Dopamine and Norepinephrine.

Thirty-two congeneric rigid adenine nucleoside derivatives containing a North (N)-methanocarba ribose substitution and a 2-arylethynyl group either enhanced (up to 760% of control) or inhibited [(125)I] methyl (1R,2S,3S)-3-(4-iodophenyl)-8-methyl-8-azabicyclo[3.2.1]octane-2-carboxylate (RTI-55) binding at the human dopamine (DA) transporter (DAT) and inhibited DA uptake.

The role of 5-HT2A, 5-HT 2C and mGlu2 receptors in the behavioral effects of tryptamine hallucinogens N,N-dimethyltryptamine and N,N-diisopropyltryptamine in rats and mice.

Rationale: Serotonin 5-HT2A and 5-HT2C receptors are thought to be the primary pharmacological mechanisms for serotonin-mediated hallucinogenic drugs, but recently there has been interest in metabotropic glutamate (mGluR2) receptors as contributors to the mechanism of hallucinogens.

Objective: The present study assesses the role of these 5-HT and glutamate receptors as molecular targets for two tryptamine hallucinogens, N,N-dimethyltryptamine (DMT) and N,N-diisopropyltryptamine (DiPT).

Methods: Drug discrimination, head twitch, and radioligand binding assays were used.

Mefloquine and psychotomimetics share neurotransmitter receptor and transporter interactions in vitro.

Rationale: Mefloquine is used for the prevention and treatment of chloroquine-resistant malaria, but its use is associated with nightmares, hallucinations, and exacerbation of symptoms of post-traumatic stress disorder. We hypothesized that potential mechanisms of action for the adverse psychotropic effects of mefloquine resemble those of other known psychotomimetics.

Objectives: Using in vitro radioligand binding and functional assays, we examined the interaction of (+)- and (-)-mefloquine enantiomers, the non-psychotomimetic anti-malarial agent, chloroquine, and several hallucinogens and psychostimulants with recombinant human neurotransmitter receptors and transporters.

Effect of Iboga alkaloids on µ-opioid receptor-coupled G protein activation.

Objective: The iboga alkaloids are a class of small molecules defined structurally on the basis of a common ibogamine skeleton, some of which modify opioid withdrawal and drug self-administration in humans and preclinical models. These compounds may represent an innovative approach to neurobiological investigation and development of addiction pharmacotherapy. In particular, the use of the prototypic iboga alkaloid ibogaine for opioid detoxification in humans raises the question of whether its effect is mediated by an opioid agonist action, or if it represents alternative and possibly novel mechanism of action.

Behavioral and neurochemical pharmacology of six psychoactive substituted phenethylamines: mouse locomotion, rat drug discrimination and in vitro receptor and transporter binding and function.

Rationale: Psychoactive-substituted phenethylamines 2,5-dimethoxy-4-chlorophenethylamine (2C-C); 2,5-dimethoxy-4-methylphenethylamine (2C-D); 2,5-dimethoxy-4-ethylphenethylamine (2C-E); 2,5-dimethoxy-4-iodophenethylamine (2C-I); 2,5-dimethoxy-4-ethylthiophenethylamine (2C-T-2); and 2,5-dimethoxy-4-chloroamphetamine (DOC) are used recreationally and may have deleterious side effects.

Objectives: This study compares the behavioral effects and the mechanisms of action of these substituted phenethylamines with those of hallucinogens and a stimulant.

Methods: The effects of these compounds on mouse locomotor activity and in rats trained to discriminate dimethyltryptamine, (-)-DOM, (+)-LSD, (±)-MDMA, and S(+)-methamphetamine were assessed.

Substituted methcathinones differ in transporter and receptor interactions.

The use of synthetic methcathinones, components of "bath salts," is a world-wide health concern. These compounds, structurally similar to methamphetamine (METH) and 3,4-methylendioxymethamphetamine (MDMA), cause tachycardia, hallucinations and psychosis. We hypothesized that these potentially neurotoxic and abused compounds display differences in their transporter and receptor interactions as compared to amphetamine counterparts.

GABAB receptor activation attenuates the stimulant but not mesolimbic dopamine response to ethanol in FAST mice.

Neural processes influenced by γ-aminobutyric acid B (GABA(B)) receptors appear to contribute to acute ethanol sensitivity, including the difference between lines of mice bred for extreme sensitivity (FAST) or insensitivity (SLOW) to the locomotor stimulant effect of ethanol. One goal of the current study was to determine whether selection of the FAST and SLOW lines resulted in changes in GABA(B) receptor function, since the lines differ in sensitivity to the GABA(B) receptor agonist baclofen and baclofen attenuates the stimulant response to ethanol in FAST mice. A second goal was to determine whether the baclofen-induced reduction in ethanol stimulation in FAST mice is associated with an attenuation of the mesolimbic dopamine response to ethanol.

Melittin initiates dopamine transporter internalization and recycling in transfected HEK-293 cells.

The dopamine transporter removes the neurotransmitter from the synapse, regulating dopamine availability. The transporter can be internalized and its function is blocked by cocaine and other ligands. Melittin inhibits dopamine transporter function and causes internalization of the recombinant transporter in stably transfected HEK-293 cells, but the specific pathways for internalization and disposition of the transporter are unknown.