Aripiprazole attenuates established behavioral sensitization induced by methamphetamine

Substance-induced schizophrenia: possible pathogenetic mechanisms

This brief report presents a narrative literature review describing potential pathogenetic mechanisms underlying the transformation of drug-induced psychoses into chronic psychotic disorders of the schizophrenic spectrum. The central role of hyperdopaminergia in the development of productive psychotic symptoms is discussed, along with the possibility of dopamine D2 receptor sensitization resulting from prolonged use of stimulant drugs. Attention is drawn to the previously described phenomenon of reverse tolerance, the study of which at genetic, molecular, neurotransmitter, and clinical levels may offer a promising approach for clinical assessment of prognosis and prevention of schizophrenia in individuals with a history of substance use.

Pharmacological Treatments for Methamphetamine Use Disorder: Current Status and Future Targets

The illicit use of the psychostimulant methamphetamine (METH) is a major concern, with overdose deaths increasing substantially since the mid-2010s. One challenge to treating METH use disorder (MUD), as with other psychostimulant use disorders, is that there are no available pharmacotherapies that can reduce cravings and help individuals achieve abstinence. The purpose of the current review is to discuss the molecular targets that have been tested in assays measuring the physiological, the cognitive, and the reinforcing effects of METH in both animals and humans. Several drugs show promise as potential pharmacotherapies for MUD when tested in animals, but fail to produce long-term changes in METH use in dependent individuals (eg, modafinil, antipsychotic medications, baclofen). However, these drugs, plus medications like atomoxetine and varenicline, may be better served as treatments to ameliorate the psychotomimetic effects of METH or to reverse METH-induced cognitive deficits. Preclinical studies show that vesicular monoamine transporter 2 inhibitors, metabotropic glutamate receptor ligands, and trace amine-associated receptor agonists are efficacious in attenuating the reinforcing effects of METH; however, clinical studies are needed to determine if these drugs effectively treat MUD. In addition to screening these compounds in individuals with MUD, potential future directions include increased emphasis on sex differences in preclinical studies and utilization of pharmacogenetic approaches to determine if genetic variances are predictive of treatment outcomes. These future directions can help lead to better interventions for treating MUD.

Angiotensin II involvement in the development and persistence of amphetamine-induced sensitization: Striatal dopamine reuptake implications

Amphetamine (AMPH) exposure induces behavioural and neurochemical sensitization observed in rodents as hyperlocomotion and increased dopamine release in response to a subsequent dose. Brain Angiotensin II modulates dopaminergic neurotransmission through its AT1 receptors (AT1-R), positively regulating striatal dopamine synthesis and release. This work aims to evaluate the AT1-R role in the development and maintenance of AMPH-induced sensitization. Also, the AT1-R involvement in striatal dopamine reuptake was analysed. The sensitization protocol consisted of daily AMPH administration for 5 days and tested 21 days after withdrawal. An AT1-R antagonist, candesartan, was administered before or after AMPH exposure to evaluate the participation of AT1-R in the development and maintenance of sensitization, respectively. Sensitization was evaluated by locomotor activity and c-Fos immunostaining. Changes in dopamine reuptake kinetics were evaluated 1 day after AT1-R blockade withdrawal treatment, with or without the addition of AMPH in vitro. The social interaction test was performed as another behavioural output. Repeated AMPH exposure induced behavioural and neurochemical sensitization, which was prevented and reversed by candesartan. The AT1-R blockade increased the dopamine reuptake kinetics. Neither the AMPH administration nor the AT1-R blockade altered the performance of social interaction. Our results highlight the AT1-R's crucial role in AMPH sensitization. The enhancement of dopamine reuptake kinetics induced by the AT1-R blockade might attenuate the neuroadaptive changes that lead to AMPH sensitization and its self-perpetuation. Therefore, AT1-R is a prominent candidate as a target for pharmacological treatment of pathologies related to dopamine imbalance, including drug addiction and schizophrenia.

Third-Generation Antipsychotics and Lurasidone in the Treatment of Substance-Induced Psychoses: A Narrative Review

This narrative review explores the efficacy and tolerability of third-generation antipsychotics (TGAs)-aripiprazole, cariprazine, brexpiprazole, and lurasidone-for the management of substance-induced psychosis (SIP). SIP is a psychiatric condition triggered by substance misuse or withdrawal, characterized by unique features distinct from those of primary psychotic disorders. These distinctive features include a heightened prevalence of positive symptoms, such as hallucinations and delusions, in addition to a spectrum of mood and cognitive disturbances. This review comprehensively investigates various substances, such as cannabinoids, cocaine, amphetamines, and LSD, which exhibit a greater propensity for inducing psychosis. TGAs exhibit substantial promise in addressing both psychotic symptoms and issues related to substance misuse. This review elucidates the distinctive pharmacological properties of each TGA, their intricate interactions with neurotransmitters, and their potential utility in the treatment of SIP. We advocate for further research to delineate the long-term effects of TGAs in this context and underscore the necessity for adopting an integrated approach that combines pharmacological and psychological interventions. Our findings underscore the intricate and multifaceted nature of treating SIP, highlighting the potential role of TGAs within therapeutic strategies.

Far-infrared Ray-mediated Antioxidant Potentials are Important for Attenuating Psychotoxic Disorders

Far-infrared ray (FIR) is an electromagnetic wave that produces various health benefits against pathophysiological conditions, such as diabetes mellitus, renocardiovascular disorders, stress, and depression etc. However, the therapeutic ap-plication on the FIR-mediated protective potentials remains to be further extended. To achieve better understanding on FIR-mediated therapeutic potentials, we summarized additional findings in the present study that exposure to FIR ameliorates stressful condition, memory impairments, drug dependence, and mitochondrial dysfunction in the central nervous system. In this review, we underlined that FIR requires modulations of janus kinase 2 / signal transducer and activator of transcription 3 (JAK2/STAT3), nuclear factor E2-related factor 2 (Nrf-2), muscarinic M1 acetylcholine receptor (M1 mAChR), dopamine D1 receptor, protein kinase C δ gene, and glutathione peroxidase-1 gene for exerting the protective potentials in response to neuropsychotoxic conditions

Comparative Evaluation of A Partial Dopamine Agonist with A Preferential D2 and D3 Receptor Antagonist on Ethanol Induced Conditioned Place Preference in Mice

Background:

The role of dopamine receptor sub-families in the rewarding and reinforcing effects of drugs of abuse has been established in numerous studies. </P><P> Objectives: In view of the extensive role of mesolimbic dopaminergic transmission in rewarding and reinforcing effect of abused drugs including ethanol, the present study evaluated three mechanistically different drugs viz a partial dopaminergic agonist (PDA, aripiprazole), preferential D3 (mixed D2/D3) receptor antagonist (nafadotride), and a preferential D2 antagonist (haloperidol), on ethanol-induced conditioned place preference (CPP) in mice. </P><P> Method: The study was carried out in Swiss strain albino mice. Ethanol (20%, 2g/kg) was used to induce CPP in mice. After the acquisition of CPP, behavioral tests (elevated plus maze and locomotor activity) were conducted and effect of drugs on expression and on reinstatement (after extinction) was studied.

Results:

We found that aripiprazole (1 and 2 mg/kg but not 0.5mg/kg), haloperidol (0.2 mg/kg), and nafadotride (4.5 mg/kg) administered for 1 week during the conditioning phase prevented acquisition, expression and reinstatement of ethanol-induced CPP. All the three drugs reduced the ethanol-induced locomotor stimulation and produced antianxiety effects in elevated plus maze following the acquisition of ethanol CPP.

Conclusion:

Partial dopaminergic agonism by aripiprazole was found to be a better strategy for normalizing dopaminergic neurotransmission in alcoholics as seen in rodents.

Involvement of dopamine D2 receptor in a single methamphetamine-induced behavioral sensitization in C57BL/6J mice

A single exposure to drugs of abuse is sufficient to induce behavioral sensitization, which is a form of long-lasting neuroplasticity. Dopamine D2 receptors are the main receptor for antipsychotic drugs, but little is known about their role in a single methamphetamine-induced behavioral sensitization. In the present study, we examined whether typical antipsychotic haloperidol and atypical antipsychotic risperidone, both targeting dopamine D2 receptor, could prevent the methamphetamine sensitization when they were given at the different phase of behavioral sensitization. A single methamphetamine exposure induced robust and reliable behavioral sensitization to the lower challenge dose of methamphetamine after 7 days of drug-free period. At doses that did not affect general locomotion, haloperidol and risperidone not only significantly attenuated methamphetamine induced hyperlocomotion, but also completely prevented the development of behavioral sensitization to methamphetamine challenge when they were pretreated before the first exposure to methamphetamine. When haloperidol and risperidone were given in the early period of transfer (2 h after the first methamphetamine exposure), they also dose-dependently attenuated the transfer to expression of methamphetamine sensitization from the hyperlocomotion. These data suggest that dopamine D2 receptors play an important role in methamphetamine sensitization, especially in protecting against the development and transfer in the earlier labile period after the methamphetamine exposure. Therefore, clinically approved dopamine D2 receptor antagonists may be useful in the treatment of methamphetamine addiction.

Pharmacotherapeutic agents in the treatment of methamphetamine dependence

INTRODUCTION

Methamphetamine use is a serious public health concern in many countries and is second to cannabis as the most widely abused illicit drug in the world. Effective management for methamphetamine dependence remains elusive and the large majority of methamphetamine users relapse following treatment. Areas covered: Progression in the understanding of the pharmacological basis of methamphetamine use has provided us with innovative opportunities to develop agents to treat dependence. The current review summarizes relevant literature on the neurobiological and clinical correlates associated with methamphetamine use. We then outline agents that have been explored for potential treatments in preclinical studies, human laboratory phase I and phase II trials over the last ten years. Expert opinion: No agent has demonstrated a broad and strong effect in achieving MA abstinence in Phase II trials. Agents with novel therapeutic targets appear promising. Advancement in MA treatment, including translation into practice, faces several clinical challenges.

Potential for targeting dopamine/DARPP-32 signaling in neuropsychiatric and neurodegenerative disorders

INTRODUCTION

Alterations in dopamine neurotransmission has been implicated in pathophysiology of neuropsychiatric and neurodegenerative disorders, and DARPP-32 plays a pivotal role in dopamine neurotransmission. DARPP-32 likely influences dopamine-mediated behaviors in animal models of neuropsychiatric and neurodegenerative disorders and therapeutic effects of pharmacological treatment. Areas covered: We will review animal studies on the biochemical and behavioral roles of DARPP-32 in drug addiction, schizophrenia and Parkinson's disease. In general, under physiological and pathophysiological conditions, DARPP-32 in D1 receptor expressing (D1R) -medium spiny neurons (MSNs) promotes dopamine/D1 receptor/PKA signaling, whereas DARPP-32 in D2 receptor expressing (D2R)-MSNs counteracts dopamine/D2 receptor signaling. However, the function of DARPP-32 is differentially regulated in acute and chronic phases of drug addiction; DARPP-32 enhances D1 receptor/PKA signaling in the acute phase, whereas DARPP-32 suppresses D1 receptor/PKA signaling in the chronic phase through homeostatic mechanisms. Therefore, DARPP-32 plays a bidirectional role in dopamine neurotransmission, depending on the cell type and experimental conditions, and is involved in dopamine-related behavioral abnormalities. Expert opinion: DARPP-32 differentially regulates dopamine signaling in D1R- and D2R-MSNs, and a shift of balance between D1R- and D2R-MSN function is associated with behavioral abnormalities. An adjustment of this imbalance is achieved by therapeutic approaches targeting DARPP-32-related signaling molecules.

Memory impairment and alterations in prefrontal cortex gamma band activity following methamphetamine sensitization

RATIONALE

Repeated methamphetamine (MA) use leads to increases in the incentive motivational properties of the drug as well as cognitive impairments. These behavioral alterations persist for some time following abstinence, and neuroadaptations in the structure and function of the prefrontal cortex (PFC) are particularly important for their expression. However, there is a weak understanding of the changes in neural firing and oscillatory activity in the PFC evoked by repeated drug use, thus complicating the development of novel treatment strategies for addiction.

OBJECTIVES

The purpose of the current study was to assess changes in cognitive and brain function following MA sensitization.

METHODS

Sensitization was induced in rats, then temporal and recognition memory were assessed after 1 or 30 days of abstinence. Electrophysiological recordings from the medial PFC were also acquired from rats whereupon simultaneous measures of oscillatory and spiking activity were examined.

RESULTS

Impaired temporal memory was observed after 1 and 30 days of abstinence. However, recognition memory was only impaired after 1 day of abstinence. An injection of MA profoundly decreased neuronal firing rate and the anesthesia-induced slow oscillation (SO) in both sensitized (SENS) and control (CTRL) rats. Strong correlations were observed between the SO and gamma band power, which was altered in SENS animals. A decrease in the number of neurons phase-locked to the gamma oscillation was also observed in SENS animals.

CONCLUSIONS

The changes observed in PFC function may play an integral role in the expression of the altered behavioral phenotype evoked by MA sensitization.

Treating methamphetamine-induced resistant psychosis with clozapine

Background. Methamphetamine-induced psychosis (MIP) in Iran has turned into a serious issue in terms of health and treatment, lacking any obvious treatment methods for its resistant cases. Aims of Case Report. In the present study, a number of two cases of treatment of MIP with clozapine, which were resistant to the treatment with other antipsychotics, have been reported. Both cases completely responded to the treatment in only 2 weeks and no signs of psychosis relapse were seen in an 8-9 follow-up. Conclusion. Because of its particular pharmacologic features, clozapine may be effective in treating MIP.

Role of MT1 melatonin receptors in methamphetamine-induced locomotor sensitization in C57BL/6 mice

RATIONALE

Melatonin modifies physiological and behavioral responses to psychostimulants, with the MT₁ and MT₂ melatonin receptors specifically implicated in facilitating methamphetamine (METH)-induced sensitization in melatonin-proficient mice.

OBJECTIVE

The objective of the study is to assess differences in locomotor sensitization after a single dose of methamphetamine in low-melatonin-expressing C57BL/6 wild-type and MT₁ receptor knockout (MT₁KO) mice, comparing with melatonin-expressing C3H/HeN mice.

METHODS

Mice received a vehicle or methamphetamine (1.2 mg/kg, i.p.) pretreatment (day 1) during the light (ZT5-9) or dark (ZT 19-21) periods in novel test arenas. Locomotor sensitization was assessed by methamphetamine challenge after an eight-day abstinence (day 9). TH protein expression was evaluated by immunofluorescence and Western blot analysis.

RESULTS

Methamphetamine pretreatment induced statistically significant locomotor sensitization upon challenge after eight-day abstinence in C3H and C57 wild-type mice during the light period. The magnitude of sensitization in C57 mice was diminished in the dark period and completely abrogated in MT₁KO mice. No differences were observed in tyrosine hydroxylase immunoreactivity in the mesolimbic dopamine system. Additional exposures to the test arenas after methamphetamine pretreatment (nights 2-6) enhanced sensitization.

CONCLUSIONS

Deletion of the MT₁ melatonin receptor abolishes sensitization induced by a single METH pretreatment. The magnitude of sensitization is also altered by time of day and contextual cues. We conclude that the MT₁ melatonin receptor is emerging as a novel target of therapeutic intervention for drug abuse disorders.

Extending therapeutic use of psychostimulants: focus on serotonin-1A receptor

INTRODUCTION

Despite a number of medicinally important pharmacological effects, the therapeutic use of psychostimulants is limited because of abuse potential and psychosis following long term use. Development of pharmacological agents for improving and extending therapeutic use of psychostimulants in narcolepsy, attention deficit hyperactivity disorder, Parkinson's disease, obesity and as cognitive enhancer is an important research imperative. In this regard, one potential target system is the 5-hydroxytryptamine (5-HT; serotonin) neurotransmitter system. The focus of the present article is to evaluate a potential role of 5-HT-1A receptor in the alleviation of abuse potential and psychosis-induced by prescription psychostimulants amphetamines and apomorphine.

METHOD

Synaptic contacts between dopamine systems and 5-HT-1A receptors are traced. Studies on serotonin-1A influences on the modulation of dopamine neurotransmission and psychostimulant-induced behavioral sensitization are accumulated.

RESULTS

Inhibition of amphetamine and apomorphine-induced behavioral sensitization by co administration of 5-HT-1A agonists cannot be explained in terms of direct activation of 5-HT-1A receptors, because activation of pre- as well as postsynaptic 5-HT-1A receptors tends to increase dopamine neurotransmission.

CONCLUSION

Long term use of amphetamine and apomorphine produces adaptive changes in 5-HT-1A receptor mediated functions, which are prevented by the co-use of 5-HT-1A agonists. In view of extending medicinal use of psychostimulants, it is important to evaluate the effects of co-use of 5-HT-1A agonists on potential therapeutic profile of amphetamine and apomorphine in preclinical research. It is also important to evaluate the functional significance of 5-HT-1A receptors on psychostimulant-induced behaviors in other addiction models such as drug self-administration and reinstatement of drug seeking behavior.

Aripiprazole for the treatment of methamphetamine dependence: a randomized, double-blind, placebo-controlled trial

AIMS

To test aripiprazole for efficacy in decreasing use in methamphetamine-dependent adults, compared to placebo.

DESIGN

Participants were randomized to receive 12 weeks of aripiprazole or placebo, with a 3-month follow-up and a platform of weekly 30-minute substance abuse counseling.

SETTING

The trial was conducted from January 2009 to March 2012 at the San Francisco Department of Public Health.

PARTICIPANTS

Ninety actively using, methamphetamine-dependent, sexually active adults were recruited from community venues.

MEASUREMENTS

The primary outcome was regression estimated reductions in weekly methamphetamine-positive urines. Secondary outcomes were study medication adherence [by self-report and medication event monitoring systems (MEMS)], sexual risk behavior and abstinence from methamphetamine.

FINDINGS

Participant mean age was 38.7 years, 87.8% were male, 50.0% white, 18.9% African American, and 16.7% Latino. Eighty-three per cent of follow-up visits and final visits were completed. By intent-to-treat, participants assigned to aripiprazole had similar reductions in methamphetamine-positive urines as participants assigned to placebo [risk ratio (RR) 0.88, 95% confidence interval (CI): 0.66-1.19, P = 0.41]. Urine positivity declined from 73% (33 of 45 participants) to 45% (18 of 40) in the placebo arm and from 77% (34 of 44) to 44% (20 of 35) in the aripiprazole arm. Adherence by MEMS and self-report was 42 and 74%, respectively, with no significant difference between arms (MEMS P = 0.31; self-report P = 0.17). Most sexual risk behaviors declined similarly among participants in both arms (all P > 0.05). There were no serious adverse events related to study drug, although participants randomized to aripiprazole reported more akathisia, fatigue and drowsiness (P < 0.05).

CONCLUSION

Compared with placebo, aripiprazole did not reduce methamphetamine use significantly among actively using, dependent adults.

Aripiprazole in the treatment of Alzheimer's disease

INTRODUCTION

Psychosis is a common and difficult to treat symptom in Alzheimer's disease (AD). It is a cause of diminished quality of life and caregiver distress. Atypical antipsychotics are frequently used for the treatment of dementia-related psychosis, despite FDA warnings because of increased mortality associated with the use of these medications in dementia patients. Aripiprazole is a newer atypical antipsychotic drug with partial agonist activity at dopamine receptors and antagonist activity at 5-HT(2A) receptors, with a low side-effect profile.

AREAS COVERED

This descriptive review gives a short overview of the pathology and epidemiology of AD, including psychotic symptoms, and describes the mode of action of aripiprazole and results of preclinical studies. Finally, randomized controlled trials evaluating the use of aripiprazole in AD-related psychosis and agitation are discussed. Whenever relevant, meta-analytical data from literature are referred to.

EXPERT OPINION

In randomized placebo-controlled clinical trials, aripiprazole shows modest efficacy in the treatment of AD-related psychosis. Neuropsychiatric symptoms alleviated were predominantly psychotic features and agitation. In individual trials, aripiprazole was generally well tolerated, serious side effects were seldom reported and included accidental injury and somnolence. Meta-analyses however demonstrated increased mortality as a class effect for atypical, but also for typical antipsychotics. No increased cardiovascular outcomes, cerebrovascular accidents, increased appetite or weight gain were demonstrated in meta-analyses for aripiprazole-treated patients with psychosis of dementia. Aripiprazole was found to induce sedation. Aripiprazole should only be used in selected patient populations resistant to non-pharmacological treatment with persisting or severe psychotic symptoms and/or agitation, and in which symptoms lead to significant morbidity, patient suffering and potential self-harm. The indication for continuing treatment should be revised regularly.

Genetic deletion of MT(1) and MT(2) melatonin receptors differentially abrogates the development and expression of methamphetamine-induced locomotor sensitization during the day and the night in C3H/HeN mice

This study explored the role of the melatonin receptors in methamphetamine (METH)-induced locomotor sensitization during the light and dark phases in C3H/HeN mice with genetic deletion of the MT(1) and/or MT(2) melatonin receptors. Six daily treatments with METH (1.2 mg/kg, i.p.) in a novel environment during the light phase led to the development of locomotor sensitization in wild-type (WT), MT(1)KO and MT(2)KO mice. Following four full days of abstinence, METH challenge (1.2 mg/kg, i.p.) triggered the expression of locomotor sensitization in METH-pretreated but not in vehicle (VEH)-pretreated mice. In MT(1)/MT(2)KO mice, the development of sensitization during the light phase was significantly reduced and the expression of sensitization was completely abrogated upon METH challenge. During the dark phase the development of locomotor sensitization in METH-pretreated WT, MT(1)KO and MT(2)KO mice was statistically different from VEH-treated controls. However, WT and MT(2)KO, but not MT(1)KO mice receiving repeated VEH pretreatments during the dark phase expressed a sensitized response to METH challenge that is of an identical magnitude to that observed upon 6 days of METH pretreatment. We conclude that exposure to a novel environment during the dark phase, but not during the light phase, facilitated the expression of sensitization to a METH challenge in a manner dependent on MT(1) melatonin receptor activation by endogenous melatonin. We suggest that MT(1) and MT(2) melatonin receptors are potential targets for pharmacotherapeutic intervention in METH abusers.

Neurite outgrowth mediated by the heat shock protein Hsp90α: a novel target for the antipsychotic drug aripiprazole

Aripiprazole is an atypical antipsychotic drug approved for the treatment of psychiatric disorders such as schizophrenia, bipolar disorder, major depressive disorder and autism. The drug shows partial agonistic activity at dopamine D(2) receptors and 5-hydroxytryptamine (5-HT) 5-HT(1A) receptors, and antagonistic activity at 5-HT(2A) receptors. However, the precise mechanistic pathways remain unclear. In this study, we examined the effects of aripiprazole on neurite outgrowth. Aripiprazole significantly potentiated nerve growth factor (NGF)-induced neurite outgrowth in PC12 cells, in a concentration-dependent manner. The 5-HT(1A) receptor antagonist WAY-100635, but not the dopamine D(2) receptor antagonist sulpiride, blocked the effects of aripiprazole, although, only partially. Specific inhibitors of inositol 1,4,5-triphosphate (IP(3)) receptors and BAPTA-AM, a chelator of intracellular Ca(2+), blocked the effects of aripiprazole. Moreover, specific inhibitors of several common signaling pathways phospholipase C-γ (PLC-γ), phosphatidylinositol-3 kinase (PI3K), mammalian target of rapamycin, p38 MAPK, c-Jun N-terminal kinase, Akt, Ras, Raf, ERK, MAPK) also blocked the effects of aripiprazole. Using proteomic analysis, we found that aripiprazole significantly increased levels of the heat shock protein Hsp90α in cultured cells. The effects of aripiprazole on NGF-induced neurite outgrowth were significantly attenuated by treatment with Hsp90α RNA interference, but not by the negative control of Hsp90α. These findings suggest that both 5-HT(1A) receptor activation and Ca(2+) signaling via IP(3) receptors, as well as their downstream cellular signaling pathways play a role in the promotion of aripiprazole-induced neurite outgrowth. Furthermore, aripiprazole-induced increases in Hsp90α protein expression may form part of the therapeutic mechanism for this drug.

Unusual effects of nicotine as a psychostimulant on ambulatory activity in mice

The present study examined the effect of nicotine, alone and in combination with various drugs that act on the CNS, on ambulatory activity, a behavioral index for locomotion, in ICR (CD-1) strain mice. Nicotine at 0.25–2 mg/kg acutely reduced ambulatory activity of ICR mice. The effect of nicotine was similar to that of haloperidol and fluphenazine but distinct from that of bupropion and methylphenidate. ICR mice developed tolerance against the inhibitory effect of nicotine on ambulatory activity when nicotine was repeatedly administered. This effect was also distinct from bupropion and methylphenidate as they produced augmentation of their ambulation-stimulating effects in ICR mice. Nicotine reduced the ambulation-stimulating effects of bupropion and methylphenidate as well as haloperidol and fluphenazine. Taken together, nicotine exhibited unusual effects as a psychostimulant on ambulatory activity in ICR mice.

Methamphetamine-associated psychosis

Methamphetamine (METH) is a frequent drug of abuse in U.S. populations and commonly associated with psychosis. This may be a factor in frequent criminal justice referrals and lengthy treatment required by METH users. Persecutory delusions and auditory hallucinations are the most consistent symptoms of METH-associated psychosis (MAP). MAP has largely been studied in Asian populations and risk factors have varied across studies. Duration, frequency and amount of use as well as sexual abuse, family history, other substance use, and co-occurring personality and mood disorders are risk factors for MAP. MAP may be unique with its long duration of psychosis and recurrence without relapse to METH. Seven candidate genes have been identified that may be associated with MAP. Six of these genes are also associated with susceptibility, symptoms, or treatment of schizophrenia and most are linked to glutamatergic neurotransmission. Animal studies of pre-pulse inhibition, attenuation of social interaction, and stereotypy and alterations in locomotion are used to study MAP in rodents. Employing various models, rodent studies have identified neuroanatomical and neurochemical changes associated with METH use. Throughout this review, we identify key gaps in our understanding of MAP and suggest potential directions for future research.

Treatment of the psychostimulant-sensitized animal model of schizophrenia

Behavioral sensitization to psychostimulants in rodents is associated with the alteration of dopaminergic neurotransmission, and has been proposed as a useful model of schizophrenia due to its progressively intensifying, easily relapsing, and long-lasting features. Pharmacological treatments that reverse the established sensitization may have potential therapeutic values for schizophrenia. The present aim is to review pharmacological treatments that induce the reversal of established sensitization to psychostimulants. In addition, we discuss possible mechanisms for the reversal of sensitization. Reversal of sensitization is induced by chronic dopamine D1 receptor agonism, D2 or D1/D2 receptor agonism combined with mild N-methyl-D-aspartate (NMDA) receptor antagonism or serotonin (5-HT(2A) or 5-HT(3) ) receptor antagonism, 5-HT(1A) receptor agonism, and 5-HT(2A) or 5-HT(3) receptor antagonism. Chronic treatments with these drugs likely adjust altered dopaminergic neurotransmission in sensitized animals. Especially, chronic dopamine D1 receptor agonism, which may adjust mesolimbic hyperdopaminergic and mesocortical hypodopaminergic functions in sensitized animals, is an attractive therapeutic approach for schizophrenia.