Amphetamine inhibits the N-methyl-D-aspartate receptor-mediated responses by directly interacting with the receptor/channel complex

MeBib Suppressed Methamphetamine Self-Administration Response via Inhibition of BDNF/ERK/CREB Signal Pathway in the Hippocampus

Methamphetamine (MA) is one of the most commonly abused drugs in the world by illegal drug users. Addiction to MA is a serious public health problem and effective therapies do not exist to date. It has also been reported that behavior induced by psychostimulants such as MA is related to histone deacetylase (HDAC). MeBib is an HDAC6 inhibitor derived from a benzimidazole scaffold. Many benzimidazole-containing compounds exhibit a wide range of pharmacological activity. In this study, we investigated whether HDAC6 inhibitor MeBib modulates the behavioral response in MA self-administered rats. Our results demonstrated that the number of active lever presses in MA self-administered rats was reduced by pretreatment with MeBib. In the hippocampus of rats, we also found MA administration promotes GluN2B, an NMDA receptor subunit, expression, which results in sequential activation of ERK/CREB/BDNF pathway, however, MeBib abrogated it. Collectively, we suggest that MeBib prevents the MA seeking response induced by MA administration and therefore, represents a potent candidate as an MA addiction inhibitor.

Comment on " In Vivo [18F]GE-179 Brain Signal Does Not Show NMDA-Specific Modulation with Drug Challenges in Rodents and Nonhuman Primates"

Schoenberger and colleagues ( Schoenberger et al. ( 2018 ) ACS Chem. Neurosci. 9 , 298 - 305 ) recently reported attempts to demonstrate specific binding of the positron emission tomography (PET) radiotracer, [¹⁸F]GE-179, to NMDA receptors in both rats and Rhesus macaques. GE-179 did not work as expected in animal models; however, we disagree with the authors' conclusion that "the [¹⁸F]GE-179 signal seems to be largely nonspecific". It is extremely challenging to demonstrate specific binding for the use-dependent NMDA receptor intrachannel ligands such as [¹⁸F]GE-179 in animals via traditional blocking, due to its low availability of target sites ( B_max^'). Schoenberger and colleagues anesthetized rats and Rhesus monkeys using isoflurane, which has an inhibitory effect on NMDA receptor function and thus would be expected to further reduce the B_max^'. The extent of glutamate release achieved in the provocation experiments is uncertain, as is whether a significant increase in NMDA receptor channel opening can be expected under anesthesia. Prior data suggest that the uptake of disubstituted arylguanidine-based ligands such as GE-179 can be reduced by phencyclidine binding site antagonists, if injection is performed in the absence of ketamine and isoflurane anesthesia, e.g., with GE-179's antecedent, CNS 5161 ( Biegon et al. ( 2007 ) Synapse 61 , 577 - 586 ), and with GMOM ( van der Doef et al. ( 2016 ) J. Cereb. Blood Flow Metab. 36 , 1111 - 1121 ). However, the extent of nonspecific uptake remains uncertain.

In Vivo [18F]GE-179 Brain Signal Does Not Show NMDA-Specific Modulation with Drug Challenges in Rodents and Nonhuman Primates

As one of the major excitatory ion channels in the brain, NMDA receptors have been a leading research target for neuroscientists, physicians, medicinal chemists, and pharmaceutical companies for decades. Molecular imaging of NMDA receptors by means of positron emission tomography (PET) with [18F]GE-179 quickly progressed to clinical PET studies, but a thorough understanding of its binding specificity has been missing and has thus limited signal interpretation. Here a preclinical study with [18F]GE-179 in rodents and nonhuman primates (NHPs) is presented in an attempt to characterize [18F]GE-179 signal specificity. Rodent PET/CT was used to study drug occupancy and functional manipulation in rats by pretreating animals with NMDA targeted blocking/modulating drug doses followed by a single bolus of [18F]GE-179. Binding competition with GE-179, MK801, PCP, and ketamine, allosteric inhibition by ifenprodil, and brain activation with methamphetamine did not alter the [18F]GE-179 brain signal in rats. In addition, multimodal imaging with PET/MRI in NHPs was used to evaluate changes in radiotracer binding as a function of pharmacological challenges. Drug-induced hemodynamic changes were monitored simultaneously using functional MRI (fMRI). Comparisons of baseline and signal after drug challenge in NHPs demonstrated that the [18F]GE-179 signal cannot be manipulated in a predictable fashion in vivo. fMRI data acquired simultaneously with PET data supported this finding and provided evidence that radiotracer delivery is not altered by blood flow changes. In conclusion, the [18F]GE-179 brain signal is not readily interpretable in the context of NMDA receptor binding on the basis of the results shown in this study.

Psychostimulants and atomoxetine alter the electrophysiological activity of prefrontal cortex neurons, interaction with catecholamine and glutamate NMDA receptors

RATIONALE

Attention-deficit hyperactivity disorder (ADHD) is the most frequently diagnosed neuropsychiatric disorder in childhood. Currently available ADHD drugs include the psychostimulants methylphenidate (MPH) and D-amphetamine (D-AMP), acting on norepinephrine and dopamine transporters/release, and atomoxetine (ATX), a selective norepinephrine uptake inhibitor. Recent evidence suggests an involvement of glutamate neurotransmission in the pathology and treatment of ADHD, via mechanisms to be clarified.

OBJECTIVE

We have investigated how ADHD drugs could modulate, through interaction with catecholamine receptors, basal and glutamate-induced excitability of pyramidal neurons in the prefrontal cortex (PFC), a region which plays a major role in control of attention and impulsivity.

METHODS

We have used the technique of extracellular single-unit recording in anaesthetised rats coupled with microiontophoresis.

RESULTS

Both MPH (1-3 mg/kg) and D-AMP (1-9 mg/kg) increased the firing activity of PFC neurons in a dopamine D1 receptor-dependent manner. ATX administration (1-6 mg/kg) also increased the firing of neurons, but this effect is not significantly reversed by D1 (SCH 23390) or alpha1 (prazosin) receptor antagonists but potentiated by alpha2 antagonist (yohimbine). All drugs induced a clear potentiation of the excitatory response of PFC neurons to the microiontophoretic application of the glutamate agonist N-methyl-D-aspartate (NMDA), but not to the glutamate agonist α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA). The potentiating effect of D-AMP on NMDA-induced activation of PFC neurons was partially reversed or prevented by dopamine D1 receptor blockade.

CONCLUSION

Our data shows that increase in excitability of PFC neurons in basal conditions and via NMDA receptor activation may be involved in the therapeutic response to ADHD drugs.

Distinct neurochemical adaptations within the nucleus accumbens produced by a history of self-administered vs non-contingently administered intravenous methamphetamine

Methamphetamine is a highly addictive psychomotor stimulant yet the neurobiological consequences of methamphetamine self-administration remain under-characterized. Thus, we employed microdialysis in rats trained to self-administer intravenous (IV) infusions of methamphetamine (METH-SA) or saline (SAL) and a group of rats receiving non-contingent IV infusions of methamphetamine (METH-NC) at 1 or 21 days withdrawal to determine the dopamine and glutamate responses in the nucleus accumbens (NAC) to a 2 mg/kg methamphetamine intraperitoneal challenge. Furthermore, basal NAC extracellular glutamate content was assessed employing no net-flux procedures in these three groups at both time points. At both 1- and 21-day withdrawal points, methamphetamine elicited a rise in extracellular dopamine in SAL animals and this effect was sensitized in METH-NC rats. However, METH-SA animals showed a much greater sensitized dopamine response to the drug challenge compared with the other groups. Additionally, acute methamphetamine decreased extracellular glutamate in both SAL and METH-NC animals at both time-points. In contrast, METH-SA rats exhibited a modest and delayed rise in glutamate at 1-day withdrawal and this rise was sensitized at 21 days withdrawal. Finally, no net-flux microdialysis revealed elevated basal glutamate and increased extraction fraction at both withdrawal time-points in METH-SA rats. Although METH-NC rats exhibited no change in the glutamate extraction fraction, they exhibited a time-dependent elevation in basal glutamate levels. These data illustrate for the first time that a history of methamphetamine self-administration produces enduring changes in NAC neurotransmission and that non-pharmacological factors have a critical role in the expression of these methamphetamine-induced neurochemical adaptations.

Inhibition of sigma-1 receptor reduces N-methyl-D-aspartate induced neuronal injury in methamphetamine-exposed and -naive hippocampi

Acute and prolonged methamphetamine (METH) exposure has been reported to moderate the function of N-methyl-d-aspartate type glutamate receptors (NMDAr) in the hippocampus. These effects have been found to be associated with enhanced NMDAr-dependent release of Ca(2+) from IP(3)-sensitive intracellular stores. The present studies were designed to extend these findings and examine the role of the endoplasmic membrane (ER) bound orphan receptor, the sigma-1 receptor, in NMDA-induced neuronal injury and METH withdrawal-potentiated NMDA-induced neuronal injury. Organotypic hippocampal slice cultures were exposed to METH (0 or 100microM) for 6 days and withdrawn for 7 days, then exposed to NMDA (0 or 5microM) for 24h. Additional cultures were also exposed to this regimen and were co-incubated with BD1047 (100microM), a specific inhibitor of ER-bound sigma-1 receptors, for the 24h NMDA exposure. Cytotoxicity was assessed by analysis of propidium iodide uptake. These studies demonstrated that protracted METH exposure and withdrawal significantly potentiated the neuronal injury produced by NMDA exposure. Further, co-exposure to BD1047 with NMDA markedly attenuated neuronal injury in METH-naïve and METH-withdrawn organotypic cultures. As a whole, these data demonstrate that prolonged METH exposure, even at non-toxic concentrations, significantly alters glutamate receptor signaling. Inhibition of sigma-1 receptor-dependent Ca(2+) release from the ER entirely prevented NMDA-induced toxicity in METH-naïve cultures and markedly reduced METH-potentiated toxicity. These findings demonstrate the importance of Ca(2+)-induced intracellular Ca(2+) release in excitotoxic insult and suggest that blockade of glutamatergic overactivity may represent a therapeutic target in the treatment of METH withdrawal.

Neurotoxic effects of methamphetamine on rat hippocampus pyramidal neurons

Methamphetamine (MAP) is known to alter behavior and cause deficits in learning and memory. While the major site of action of MAP is on mesolimbic dopaminergic pathways, the effects on learning and memory raise the possibility of important actions in the hippocampus. We have studied electrophysiologic and morphologic effects of MAP in the CA1 region of hippocampus from young male rats chronically exposed to MAP, male rats exposed during gestation only and the effects of bath perfusion of MAP onto brain slices from control rats. Pyramidal neurons in brain slices from chronically exposed rats had reduced membrane potential and membrane resistance. Long-term potentiation (LTP) was reduced as compared to control, but when MAP was acutely perfused over control slices the amplitude of LTP was increased. LTP in young adult animals that had been gestationally exposed to MAP showed reduced LTP as compared to controls. Morphologically CA1 pyramidal neurons in chronically exposed animals showed a high prevalence of extensive blebbing of dendrites. We conclude that the NMDA receptor and the process of LTP are also targets of MAP dysfunction, at least in the hippocampus.

The dysbindin gene (DTNBP1) is associated with methamphetamine psychosis

BACKGROUND

The dysbindin (DTNBP1 [dystrobrevin-binding protein 1]) gene has repeatedly been shown to be associated with schizophrenia across diverse populations. One study also showed that risk haplotypes were shared with a bipolar disorder subgroup with psychotic episodes, but not with all cases. DTNBP1 may confer susceptibility to psychotic symptoms in various psychiatric disorders besides schizophrenia.

METHODS

Methamphetamine psychosis, the psychotic symptoms of which are close to those observed in schizophrenia, was investigated through a case (n = 197)-control (n = 243) association analyses of DTNBP1.

RESULTS

DTNBP1 showed significant associations with methamphetamine psychosis at polymorphisms of P1635 (rs3213207, p = .00003) and SNPA (rs2619538, p = .049) and the three-locus haplotype of P1655 (rs2619539)-P1635-SNPA (permutation p = .0005). The C-A-A haplotype, which was identical to the protective haplotype previously reported for schizophrenia and psychotic bipolar disorders, was a protective factor (p = .0013, odds ratio [OR] = .62, 95% confidence interval [CI] .51-.77) for methamphetamine psychosis. The C-G-T haplotype was a risk for methamphetamine psychosis (p = .0012, OR = 14.9, 95% CI 3.5-64.2).

CONCLUSIONS

Our genetic evidence suggests that DTNBP1 is involved in psychotic liability not only for schizophrenia but also for other psychotic disorders, including substance-induced psychosis.

Characterization of interactions between phencyclidine and amphetamine in rodent prefrontal cortex and striatum: Implications in NMDA/glycine-site-mediated dopaminergic dysregulation and dopamine transporter function

N-Methyl-D-aspartate (NMDA) antagonists induced behavioral and neurochemical changes in rodents that serve as animal models of schizophrenia. Chronic phencyclidine (PCP, 15 mg/(kg day) for 3 weeks via Alzet osmotic pump) administration enhances the amphetamine (AMPH)-induced dopamine (DA) efflux in prefrontal cortex (PFC), similar to that observed in schizophrenia. NMDA/glycine-site agonists, such as glycine (GLY), administered via dietary supplementation, reverse the enhanced effect. The present study investigated mechanisms of glycine-induced reversal of PCP-induced stimulation of AMPH-induced DA release, using simultaneous measurement of DA and AMPH in brain microdialysate, as well as peripheral and tissue AMPH levels. PCP treatment, by itself, increased peripheral and central AMPH levels, presumably via interaction with hepatic enzymes (e.g. cytochrome P450 CYP2C11). GLY (16% diet) had no effect on peripheral AMPH levels in the presence of PCP. Nevertheless, GLY significantly reduced extracellular/tissue AMPH ratios in both PFC and striatum (STR), especially following PCP administration, suggesting a feedback mediated effect on the dopamine transporter. GLY also inhibited acute AMPH (5 mg/kg)-induced DA release in PFC, but not STR. These findings suggest that GLY may modulate DA release in brain by producing feedback regulation of dopamine transporter function, possibly via potentiation of NMDA-stimulated GABA release and presynaptic GABAB receptor activation. The present studies also demonstrate pharmacokinetic interaction between AMPH and PCP, which may be of both clinical and research relevance.

Potentiation of N-methyl-D-aspartate receptor-mediated neuronal injury during methamphetamine withdrawal in vitro requires co-activation of IP3 receptors

Recent findings suggest that methamphetamine (METH) functions acutely to inhibit N-methyl-d-aspartate (NMDA) receptor function. Protracted withdrawal from METH exposure may increase the sensitivity of NMDA receptors to agonist exposure, promoting neuronal excitability. However, the relevance of METH effects on NMDA receptor activity with regard to neuronal viability has not been fully studied. The present studies examined the effects of protracted METH exposure (6 or 7 days; 1.0-100 microM) and withdrawal (1 or 7 days) on NMDA receptor-dependent neurotoxicity, determined with use of the non-vital fluorescent marker propidium iodide, in organotypic slice cultures of male and female rats. Prolonged exposure to METH (100 microM) produced only modest toxicity in the granule cell layer of the dentate gyrus. Withdrawal from METH exposure (1 or 7 days) did not produce overt neuronal injury in any region of slice cultures. Exposure to NMDA (5 microM) produced marked neurotoxicity in the CA1 pyramidal cell layer. Neither co-exposure to METH nor 1 day of METH withdrawal in combination with NMDA exposure altered NMDA-induced neurotoxicity. In contrast, protracted withdrawal from METH exposure (7 days) was associated with a marked (approximately 400%) increase in NMDA-induced neurotoxicity in CA1 region pyramidal cells. This potentiation of neurotoxicity was prevented by co-exposure to the selective NMDA receptor antagonist 5-2-amino-5-phosphonovaleric acid (20 microM) and was markedly attenuated by co-exposure of slices to xestospongin C (1 microM), an antagonist of IP(3) receptors. The results of the present studies suggest that long-term METH withdrawal functionally sensitizes the NMDA receptor to agonist exposure and requires the co-activation of NMDA and IP(3) receptors.

Methamphetamine exposure antagonizes N-methyl-D-aspartate receptor-mediated neurotoxicity in organotypic hippocampal slice cultures

Glutamatergic systems have been increasingly recognized as mediators of methamphetamine's (METH) pharmacological effects though little is known about the means by which METH interacts with glutamate receptors. The present studies examined effects of METH (0.1-100 microM) on [3H]MK-801 binding to membranes prepared from adult rat cortex, hippocampus and cerebellum, as well as the neurotoxicity produced by 24-h exposure to N-methyl-D-aspartate (5-10 microM; NMDA) employing organotypic hippocampal slice cultures of neonatal rat. Co-incubation of [3H]MK-801 with METH (0.1-100 microM) did not reduce dextromethorphan (1 mM)-displaceable ligand binding. Exposure of slice cultures to NMDA for 24-h produced increases in uptake of the non-vital fluorescent marker propidium iodide (PI) of 150-500% above control levels, most notably, in the CA1 region pyramidal cell layer. Co-exposure to METH (>1.0 microM) with NMDA (5 microM) reduced PI uptake by approximately 50% in each subregion, though the CA1 pyramidal cell layer was markedly more sensitive to the protective effects of METH exposure. In contrast, METH exposure did not reduce PI uptake stimulated by 24-h exposure to 10 microM NMDA. Co-exposure to the NMDA receptor antagonist D-2-amino-5-phosphonovaleric acid (20 microM) prevented toxicity produced by exposure to 5 or 10 microM NMDA. These findings indicate that the pharmacological effects of short-term METH exposure involve inhibition of NMDA receptor-mediated neuronal signaling, not reflective of direct channel inhibition at an MK-801-sensitive site.

Lipoteichoic acid induces prostaglandin E2 release and cyclooxygenase-2 synthesis in rat cortical neuronal cells: Involvement of PKCε and ERK activation

Inflammatory processes occur in the central nervous system (CNS) through mechanisms that differ from other inflammation, and with distinct cellular effects. Neuronal injury in bacterial meningitis is not a monocausal event, but is mediated by several factors. One is possible direct toxicity of bacterial compounds. Lipoteichoic acid (LTA) is a cell wall component unique to Gram-positive bacteria. In a previous report, LTA could interact with CD14 to induce NF-kappaB activation, which is involved in transcriptional regulation of adhesion molecules, enzymes and cytokines. Although there are many aspects to neuroinflammation, the pathways involving the cyclooxygenase (COX)-2 and subsequent generation of prostaglandin clearly play a role. LTA has been shown to stimulate inflammatory responses in a number of in vivo and in vitro experimental models. However, little was known about the molecular mechanisms of LTA implicated in inflammatory responses in neurons. In this study, we characterized the mechanisms underlying signaling transduction in rat cortical neuronal cells challenged by LTA. Here, we first showed that in rat cortical neuronal cells, LTA might activate protein tyrosine kinase (PTK), phosphatidylcholine-specific phospholipase C (PC-PLC), and phosphatidylinositol-specific phospholipase C (PI-PLC) to induce protein kinase Cepsilon activation, which in turn induces extracellular signal-regulated kinase (ERK) activation, finally inducing PGE(2) release and COX-2 synthesis.

Effects of acute amphetamine administration on AMPA-mediated synaptic activity and expression of AMPA receptor subunit 2 of brain neurons

We investigated the role of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor (AMPAR) in mechanisms underlying the action of amphetamine (Amph) on brain neurons, for AMPAR has been proposed to participate in psychotic and neurodegenerative disorders. In the cultured rat brain cortical neurons pretreated with 1 microM Amph for 1 h, the accumulation of 45Ca2+ driven by 10 min incubation with 100 microM AMPA was reduced by about 36%. This Amph-induced decrease seems to involve L-type voltage-gated Ca2+ channels, because the AMPA-induced 45Ca2+ uptake was blocked by 70% and 80%, respectively, for untreated and Amph-treated neurons in the presence of nifedipine (1 microM), an antagonist to L-type calcium channels. Whole-cell, patch-clamp recording revealed that AMPA-elicited current amplitude became 26% lower than the control in Amph-treated cultured neurons. Moreover, Amph treatment down-regulated the level of flip-form glutamate receptor 2 (GluR2) mRNA by 27% in cultured neurons but did not change the expression of GluR2 proteins and flop-form mRNA, as detected by quantitative immunocytochemistry and in situ hybridization. In contrast, in postnatal day 4 rats at 1 h after receiving one intraperitoneal injection of 5 mg/kg of Amph, levels of flip GluR2 mRNA were up-regulated by 13% and 18% in neurons of motor cortex layer 5 and pyramidal neurons of hippocampal CA3, respectively. The data suggest that acute action of Amph on brain neurons is possibly associated with decreased AMPA-mediated Ca2+ influx and current amplitude, as well as modified expression of the GluR2 mRNA.