Heterozygous and homozygous gene knockout of the 5-HT1B receptor have different effects on methamphetamine-induced behavioral sensitization.

The psychostimulant drug methamphetamine (METH) causes euphoria in humans and locomotor hyperactivity in rodents by acting on the mesolimbic dopamine (DA) pathway and has severe abuse and addiction liability. Behavioral sensitization, an increased behavioral response to a drug with repeated administration, can persist for many months after the last administration. Research has shown that the serotonin 1B (5-HT1B) receptor plays a critical role in the development and maintenance of drug addiction, as well as other addictive behaviors. This study examined the role of 5-HT1B receptors in METH-induced locomotor sensitization using 5-HT1B knockout (KO) mice. To clarify the action of METH in 5-HT1B KO mice the effects of METH on extracellular levels of DA (DAec) and 5-HT (5-HTec) in the caudate putamen (CPu) and the nucleus accumbens (NAc) were examined. Locomotor sensitization and extracellular monoamine levels were determined in wild-type mice (5-HT1B +/+), heterozygous 5-HT1B receptor KO (5-HT1B +/-) mice and homozygous 5-HT1B receptor KO mice (5-HT1B -/-). Behavioral sensitization to METH was enhanced in 5-HT1B -/- mice compared to 5-HT1B +/+ mice but was attenuated in 5-HT1B +/- mice compared to 5-HT1B +/+ and 5-HT1B -/- mice. In vivo, microdialysis demonstrated that acute administration of METH increases DAec levels in the CPu and NAc of 5-HT1B KO mice compared to saline groups. In 5-HT1B +/- mice, METH increased 5-HTec levels in the CPu, and DAec levels in the NAc were higher than in others.5-HT1B receptors play an important role in regulating METH-induced behavioral sensitization.

Cadherin 13: human cis-regulation and selectively-altered addiction phenotypes and cerebral cortical dopamine in knockout mice.

The cadherin 13 (CDH13) gene encodes a cell adhesion molecule likely to influence development and connections of brain circuits that modulate addiction, locomotion and cognition, including those that involve midbrain dopamine neurons. Human CDH13 mRNA expression differs by more than 80% in postmortem cerebral cortical samples from individuals with different CDH13 genotypes, supporting examination of mice with altered Cdh13 expression as models for common human variation at this locus. Constitutive cdh13 knockout mice display evidence for changed cocaine reward: shifted dose response relationship in tests of cocaine-conditioned place preference using doses that do not alter cocaine conditioned taste aversion. Reduced adult Cdh13 expression in conditional knockouts also alters cocaine reward in ways that correlate with individual differences in cortical Cdh13 mRNA levels. In control and comparison behavioral assessments, knockout mice display modestly-quicker acquisition of rotarod and water maze tasks, with a trend toward faster acquisition of 5 choice serial reaction time tasks that otherwise displayed no genotype-related differences. They display significant differences in locomotion in some settings, with larger effects in males. In assessments of brain changes that might contribute to these behavioral differences, there are selective alterations of dopamine levels, dopamine/metabolite ratios, dopaminergic fiber densities and mRNA encoding the activity dependent transcription factor npas4 in cerebral cortex of knockout mice. These novel data and previously reported human associations of CDH13 variants with addiction, individual differences in responses to stimulant administration and attention deficit hyperactivity disorder (ADHD) phenotypes suggest that levels of CDH13 expression, through mechanisms likely to include effects on mesocortical dopamine, influence stimulant reward and may contribute modestly to cognitive and locomotor phenotypes relevant to ADHD.

Attenuated methamphetamine-induced locomotor sensitization in serotonin transporter knockout mice is restored by serotonin 1B receptor antagonist treatment.

Repeated administration of methamphetamine (METH) enhances acute locomotor responses to METH administered in the same context, a phenomenon termed as 'locomotor sensitization'. Although many of the acute effects of METH are mediated by its influences on the compartmentalization of dopamine, serotonin systems have also been suggested to influence the behavioral effects of METH in ways that are not fully understood. The present experiments examined serotonergic roles in METH-induced locomotor sensitization by assessing: (a) the effect of serotonin transporter (SERT; Slc6A4) knockout (KO) on METH-induced locomotor sensitization; (b) extracellular monoamine levels in METH-treated animals as determined by in-vivo microdialysis; and (c) effects of serotonin (5-HT) receptor antagonists on METH-induced behavioral sensitization, with focus on effects of the 5-HT1B receptor antagonist SB 216641 and a comparison with the 5-HT2 receptor antagonist ketanserin. Repeated METH administration failed to induce behavioral sensitization in homozygous SERT KO (SERT-/-) mice under conditions that produced substantial sensitization in wild-type or heterozygous SERT KO (SERT+/-) mice. The selective 5-HT1B antagonist receptor SB 216641 restored METH-induced locomotor sensitization in SERT-/- mice, whereas ketanserin was ineffective. METH-induced increases in extracellular 5-HT (5-HTex) levels were substantially reduced in SERT-/- mice, although SERT genotype had no effect on METH-induced increases in extracellular dopamine. These experiments demonstrate that 5-HT actions, including those at 5-HT1B receptors, contribute to METH-induced locomotor sensitization. Modulation of 5-HT1B receptors might aid therapeutic approaches to the sequelae of chronic METH use.

Methylone-induced hyperthermia and lethal toxicity: role of the dopamine and serotonin transporters.

Methylone (2-methylamino-1-[3,4-methylenedioxy-phenyl]propan-1-one), an amphetamine analog, has emerged as a popular drug of abuse worldwide. Methylone induces hyperthermia, which is thought to contribute toward the lethal consequences of methylone overdose. Methylone has been assumed to induce hyperthermic effects through inhibition of serotonin and/or dopamine transporters (SERT and DAT, respectively). To examine the roles of each of these proteins in methylone-induced toxic effects, we used SERT and DAT knockout (KO) mice and assessed the hyperthermic and lethal effects caused by a single administration of methylone. Methylone produced higher rates of lethal toxicity compared with other amphetamine analogs in wild-type mice. Compared with wild-type mice, lethality was significantly lower in DAT KO mice, but not in SERT KO mice. By contrast, only a slight diminution in the hyperthermic effects of methylone was observed in DAT KO mice, whereas a slight enhancement of these effects was observed in SERT KO mice. Administration of the selective D1 receptor antagonist SCH 23390 and the D2 receptor antagonist raclopride reduced methylone-induced hyperthermia, but these drugs also had hypothermic effects in saline-treated mice, albeit to a smaller extent than the effects observed in methylone-treated mice. In contradistinction to 3,4-methylenedioxymethamphetamine, which induces its toxicity through SERT and DAT, these data indicate that DAT, but not SERT, is strongly associated with the lethal toxicity produced by methylone, which did not seem to be dependent on the hyperthermic effects of methylone. DAT is therefore a strong candidate molecule for interventions aimed at preventing acute neurotoxic and lethal effects of methylone.

Development of Liquid Chromatography-Tandem Mass Spectrometry Analytical Methods for the Study of Whole-Body, Head, and Trunk Uptake and Elimination of Methamphetamine in 5-Day Postfertilization Zebrafish Larvae Using the Quick, Easy, Cheap, Effective, Rugged, and Safe Technique.

Synthetic cathinones are drugs of abuse substituted for amphetamine-like stimulant drugs such as methamphetamine. In this study, methamphetamine was studied as a prototypical amphetamine-like drug as a first step toward establishing methods to study this entire drug class. The internal concentration of methamphetamine in zebrafish larvae was determined using matrix-matched calibration along with extraction and purification of samples using the quick, easy, cheap, effective, rugged, and safe technique in liquid chromatography-tandem mass spectrometry. Whole-body and head/trunk uptake and elimination in 5-day postfertilization zebrafish larvae were determined. A gradient method was developed using 5 mM ammonium formate with 0.1% formic acid and methanol with 0.1% formic acid as mobile phases, 10 min of total run time, and a 0.3 mL/min flow rate. The limit of quantification was 60 ng/mL, linearity with r2 = 0.9991, and recovery values from 92% to 120%. The internal concentration of methamphetamine was quantifiable in whole-body homogenates within 15 min of uptake analysis. The internal concentration increased with time, whereas a biphasic elimination pattern was shown. With increasing length of exposure, a higher accumulation of drugs was found in the head than in the trunk.

Optimism Bias, Pessimism Bias, Magical Beliefs, and Conspiracy Theory Beliefs Related to COVID-19 among the Jordanian Population.

The outbreak of the novel SARS-CoV-2 virus has an enormous impact on health. People's views about the virus impact public health efforts to mitigate the pandemic. In this study, we measured misconceptions toward coronavirus in the Jordanian population; 2,544 participants from the Jordanian population completed an online survey. Questions in the survey addressed misconceptions divided into four categories: optimism bias, pessimism bias, magical beliefs, and conspiracy theory beliefs. Questions were evaluated on a Likert scale, and average/median scores for each category were evaluated ("one" high misconception to "five" low misconception). Overall, the most common misconceptions involved conspiracy theory beliefs (2.68 ± 0.83), whereas the least common involved magical beliefs (2.25 ± 0.75). Females had more misconceptions than males (2.52 versus 2.47, P = 0.04). Participants who had attended a lecture on coronavirus, had a higher level of education, worked in a medical field, lived in urban area, or resided in Amman or northern Jordan had fewer misconceptions about SARS-CoV-2/COVID-19 (2.64, 2.34, 2.33, 2.50 and 2.50 versus 2.53, 2.73, 2.72, 2.64, and 2.66, respectively, P < 0.001). The use of social media appeared to be an important factor influencing the likelihood of false beliefs (2.61 versus 2.38, P < 0.001). Understanding of the factors influencing public perceptions surrounding the SARS-CoV-2/COVID-19 pandemic will help public health authorities improve public understanding and compliance with public health recommendations directed at combatting the virus, including the use of surgical masks, thorough handwashing, and avoiding close contact. These messages will be better received by the public through correcting misconceptions surrounding COVID-19.

Dual actions of 5-MeO-DIPT at the serotonin transporter and serotonin 5-HT1A receptor in the mouse striatum and prefrontal cortex.

AIMS: 5-Methoxy-N,N-diisopropyltryptamine (5-MeO-DIPT) is a synthetic orally active hallucinogenic tryptamine analogue. The present study examined whether the effects of 5-MeO-DIPT involve the serotonin transporter (SERT) and serotonin 5-hydroxytryptamine-1A (5-HT1A ) receptor in the striatum and prefrontal cortex (PFC). METHODS: We investigated the effects of 5-MeO-DIPT on extracellular 5-HT (5-HTex ) and dopamine (DAex ) levels in the striatum and PFC in wildtype and SERT knockout (KO) mice using in vivo microdialysis, and for comparison the effects of the 5-HT1A receptor antagonist WAY100635 and the 5-HT1A receptor agonist 8-OH-DPAT on 5-HTex . RESULTS: 5-MeO-DIPT decreased 5-HTex levels in the striatum, but not PFC. In SERT-KO mice, 5-MeO-DIPT did not affect 5-HTex levels in the striatum or PFC. In the presence of WAY100635, 5-MeO-DIPT substantially increased 5-HTex levels, suggesting that 5-MeO-DIPT acts on SERT and these effects are masked by its 5-HT1A actions in the absence of WAY100635. 8-OH-DPAT decreased 5-HTex levels in the striatum and PFC in wildtype mice. WAY100635 antagonized the 8-OH-DPAT-induced decrease in 5-HTex levels. In SERT-KO mice, 8-OH-DPAT did not decrease 5-HTex levels in the striatum and PFC. 5-MeO-DIPT dose-dependently increased DAex levels in the PFC, but not striatum, in wildtype and SERT-KO mice. The increase in DAex levels that was induced by 5-MeO-DIPT was not antagonized by WAY100635. CONCLUSION: 5-MeO-DIPT influences both 5-HTex and DAex levels in the striatum and PFC. 5-MeO-DIPT dually acts on SERT and 5-HT1A receptors so that elevations in 5-HTex levels produced by reuptake inhibition are limited by actions of the drug on 5-HT1A receptors.

Lithium Pharmacology and a Potential Role of Lithium on Methamphetamine Abuse and Dependence.

BACKGROUND: The effectiveness of lithium salts in neuropsychiatric disorders such as bipolar disorder, Alzheimer's disease, and treatment-resistant depression has been documented in an extensive scientific literature. Lithium inhibits inositol monophosphatase, inositol polyphosphate 1- phosphatase, and glycogen synthase kinase-3 and decreases expression level of tryptophan hydroxylase 2, conceivably underlying the mood stabilizing effects of lithium, as well as procognitive and neuroprotective effects. However, the exact molecular mechanisms of action of lithium on mood stabilizing and pro-cognitive effects in humans are still largely unknown. OBJECTIVE: On the basis of the known aspects of lithium pharmacology, this review will discuss the possible mechanisms underlying the therapeutic effects of lithium on positive symptoms of methamphetamine abuse and dependence. CONCLUSION: It is possible that lithium treatment reduces the amount of newly synthesized phosphatidylinositol, potentially preventing or reversing neuroadaptations contributing to behavioral sensitization induced by methamphetamine. In addition, it is suggested that exposure to repeated doses of methamphetamine induces hyperactivation of glycogen synthase kinase-3ß in the nucleus accumbens and in dorsal hippocampus, resulting in a long-term alterations in synaptic plasticity underlying behavioral sensitization as well as other behavioral deficits in memory-related behavior. Therefore it is clear that glycogen synthase kinase-3ß inhibitors can be considered as a potential candidate for the treatment of methamphetamine abuse and dependence.

Larger Numbers of Glial and Neuronal Cells in the Periaqueductal Gray Matter of µ-Opioid Receptor Knockout Mice.

Background: µ-opioid receptor knockout (MOP-KO) mice display baseline hyperalgesia. We have recently identified changes in tissue volume in the periaqueductal gray matter (PAG) using magnetic resonance imaging voxel-based morphometry. Changes in the structure and connectivity of this region might account for some behavior phenotypes in MOP-KO mice, including hyperalgesia. Methods: Adult male MOP-KO and wild-type (WT) mice were studied. Immunohistochemistry was performed to detect microglia, astrocytes, and neurons in the PAG using specific markers: ionized calcium-binding adaptor molecule 1 (Iba-1) for microglia, glial fibrillary acidic protein (GFAP) for astrocytes, and the neuronal nuclei antigen (NeuN; product of the Rbfox3 gene) for neurons, respectively. Cell counting was performed in the four parallel longitudinal columns of the PAG (dorsomedial, dorsolateral, lateral, and ventrolateral) at three different locations from bregma (-3.5, -4.0, and -4.5 mm). Results: The quantitative analysis showed larger numbers of well-distributed Iba1-IR cells (microglia), NeuN-IR cells (neurons), and GFAP-IR areas (astrocytes) at all the anatomically distinct regions examined, namely, the dorsomedial (DM) PAG, dorsolateral (DL) PAG, lateral (L) PAG, and ventrolateral (VL) PAG, in MOP-KO mice than in control mice. Conclusions: The cellular changes in the PAG identified in this paper may underlie aspects of the behavioral alterations produced by MOP receptor deletion, and suggest that alterations in the cellular structure of the PAG may contribute to hyperalgesic states.

Research Domain Criteria versus DSM V: How does this debate affect attempts to model corticostriatal dysfunction in animals?

For decades, the nosology of mental illness has been based largely upon the descriptions in the Diagnostic and Statistical Manual of the American Psychiatric Association (DSM). A recent challenge to the DSM approach to psychiatric nosology from the National Institute on Mental Health (USA) defines Research Domain Criteria (RDoC) as an alternative. For RDoC, psychiatric illnesses are not defined as discrete categories, but instead as specific behavioral dysfunctions irrespective of DSM diagnostic categories. This approach was driven by two primary weaknesses noted in the DSM: (1) the same symptoms occur in very different disease states; and (2) DSM criteria lack grounding in the underlying biological causes of mental illness. RDoC intends to ground psychiatric nosology in those underlying mechanisms. This review addresses the suitability of RDoC vs. DSM from the view of modeling mental illness in animals. A consideration of all types of psychiatric dysfunction is beyond the scope of this review, which will focus on models of conditions associated with frontostriatal dysfunction.