Decreased dopamine activity predicts relapse in methamphetamine abusers.

Studies in methamphetamine (METH) abusers showed that the decreases in brain dopamine (DA) function might recover with protracted detoxification. However, the extent to which striatal DA function in METH predicts recovery has not been evaluated. Here we assessed whether striatal DA activity in METH abusers is associated with clinical outcomes. Brain DA D2 receptor (D2R) availability was measured with positron emission tomography and [(11)C]raclopride in 16 METH abusers, both after placebo and after challenge with 60 mg oral methylphenidate (MPH) (to measure DA release) to assess whether it predicted clinical outcomes. For this purpose, METH abusers were tested within 6 months of last METH use and then followed up for 9 months of abstinence. In parallel, 15 healthy controls were tested. METH abusers had lower D2R availability in caudate than in controls. Both METH abusers and controls showed decreased striatal D2R availability after MPH and these decreases were smaller in METH than in controls in left putamen. The six METH abusers who relapsed during the follow-up period had lower D2R availability in dorsal striatum than in controls, and had no D2R changes after MPH challenge. The 10 METH abusers who completed detoxification did not differ from controls neither in striatal D2R availability nor in MPH-induced striatal DA changes. These results provide preliminary evidence that low striatal DA function in METH abusers is associated with a greater likelihood of relapse during treatment. Detection of the extent of DA dysfunction may be helpful in predicting therapeutic outcomes

DEVELOPMENT AND PRECLINICAL EVALUATION OF LONG-LASTING COCAINE HYDROLASES FOR COCAINE OVERDOSE AND COCAINE USE DISORDER TREATMENT

Cocaine is a plant-based illicit drug commonly involved in substance use disorder. Although cocaine overdose and cocaine use disorders cause adverse health consequences to individuals and the economic burden on their family and society, there are no FDA (Food and Drug Administration) approved medications for treatment. Recently, it has been recognized that delivery of cocaine hydrolase (CocH) is a promising therapeutic strategy. Human butyrylcholinesterase (hBChE), the primary enzyme involved in cocaine metabolism in human, have advantages over other candidates for the development of CocH. Previous studies in our laboratory have designed and characterized hBChE mutants that have ~4,000-fold improved catalytic efficiency against naturally occurring (-)-cocaine as compared to the wild-type hBChE. Besides the catalytic efficiency, the biological half-life is another essential factor that influences the desired therapeutic value in the long-term treatment of cocaine use disorder. In order to provide prolonged effects to reduce administration frequency in clinical use, efforts have been made to increase the retention time of CocHs in blood circulation by fusing CocHs with other thermostable proteins or their mutants, including human serum albumin (Albu) or the Fc region of the human IgG (Fc). In this dissertation, we demonstrated the clinical potential and the benefits of long-lasting CocHs for cocaine overdose treatment. We used rodent models to show the ability of AlbuCocH1 to block or reverse manifestations of toxic effects of cocaine. In addition, a concomitant LC-MS/MS-based analysis was conducted to investigate the pharmacokinetic profile of a lethal dose of cocaine with the presence of AlbuCocH1. These experimental data demonstrated AlbuCocH1 as an effective cocaine detoxification agent by accelerating the metabolism of cocaine. In order to examine the potential therapeutic value of Fc-fused CocHs in the treatment of cocaine use disorder, we conducted a series of behavioral experiments in rats to evaluate the effectiveness and duration of Fc-fused CocHs in blocking or attenuating cocaine-induced psychostimulant and discriminative stimulus effects. In addition, the intravenous self-administration model was used to investigate the long-term effectiveness of Fc-fused CocHs in blocking or attenuating the reinforcing effects of cocaine. It has been shown that a single dose of E30-6-Fc (3 mg/kg) was able to effectively alter the cocaine dose-response curve and attenuate the reinforcing efficacy of cocaine for at least a month in both male and female rats. In summary, AlbuCocH1 (TV-1380), which failed to meet the primary efficacy endpoint in clinical trials for facilitating abstinence in cocaine-dependent subjects with a weekly dosing schedule (due to the short biological half-life), is more suitable to be developed as a cocaine detoxification agent. On the contrary, the newly designed Fc-fused CocH (e.g. CocH3-Fc, E30-6-Fc) with higher catalytic efficiency and longer biological half-life will be beneficial for long-term abstinence management in cocaine-dependent individuals

Chronic methamphetamine effects on brain structure and function in rats

Methamphetamine (MA) addiction is a growing epidemic worldwide. Chronic MA use has been shown to lead to neurotoxicity in rodents and humans. Magnetic resonance imaging (MRI) studies in MA users have shown enlarged striatal volumes and positron emission tomography (PET) studies have shown decreased brain glucose metabolism (BGluM) in the striatum of detoxified MA users. The present study examines structural changes of the brain, observes microglial activation, and assesses changes in brain function, in response to chronic MA treatment. Rats were randomly split into three distinct treatment groups and treated daily for four months, via i.p. injection, with saline (controls), or low dose (LD) MA (4 mg/kg), or high dose (HD) MA (8 mg/kg). Sixteen weeks into the treatment period, rats were injected with a glucose analog, [18F] fluorodeoxyglucose (FDG), and their brains were scanned with micro-PET to assess regional BGluM. At the end of MA treatment, magnetic resonance imaging at 21T was performed on perfused rats to determine regional brain volume and in vitro [3H]PK 11195 autoradiography was performed on fresh-frozen brain tissue to measure microglia activation. When compared with controls, chronic HD MA-treated rats had enlarged striatal volumes and increases in [3H]PK 11195 binding in striatum, the nucleus accumbens, frontal cortical areas, the rhinal cortices, and the cerebellar nuclei. FDG microPET imaging showed that LD MA-treated rats had higher BGluM in insular and somatosensory cortices, face sensory nucleus of the thalamus, and brainstem reticular formation, while HD MA-treated rats had higher BGluM in primary and higher order somatosensory and the retrosplenial cortices, compared with controls. HD and LD MA-treated rats had lower BGluM in the tail of the striatum, rhinal cortex, and subiculum and HD MA also had lower BGluM in hippocampus than controls. These results corroborate clinical findings and help further examine the mechanisms behind MA-induced neurotoxicity

Brain dysfunctions and neurotoxicity induced by psychostimulants in experimental models and humans: an overview of recent findings

Preclinical and clinical studies indicate that psychostimulants, in addition to having abuse potential, may elicit brain dysfunctions and/or neurotoxic effects. Central toxicity induced by psychostimulants may pose serious health risks since the recreational use of these substances is on the rise among young people and adults. The present review provides an overview of recent research, conducted between 2018 and 2023, focusing on brain dysfunctions and neurotoxic effects elicited in experimental models and humans by amphetamine, cocaine, methamphetamine, 3,4-methylenedioxymethamphetamine, methylphenidate, caffeine, and nicotine. Detailed elucidation of factors and mechanisms that underlie psychostimulant-induced brain dysfunction and neurotoxicity is crucial for understanding the acute and enduring noxious brain effects that may occur in individuals who use psychostimulants for recreational and/or therapeutic purposes

The effects of vasopressin and oxytocin on methamphetamine : induced place preference behaviour in rats.

Thesis (M.Med.Sc.)-University of KwaZulu-Natal, Westville, 2012.Methamphetamine is a highly addictive stimulant drug whose illicit use and resultant addiction has become an alarming global phenomenon. The mesolimbic dopaminergic system in the brain, originating in the ventral tegmental area and terminating in the nucleus accumbens, has been shown to be central to the neurobiology of addiction and the establishment of addictive behaviour. This pathway, as part of the reward system of the brain, has also been shown to be important in classical conditioning, which is a learnt response. This common pathway has supported theories suggesting addiction as a case of maladaptive associative learning. Within the modulation of learning and memory, the neurohypophyseal hormones vasopressin and oxytocin have been seen to play a vital role. Vasopressin exerts a long- term facilitatory effect on learning and memory processes. Studies have shown that the stress responsive AVP V1b receptor systems are a critical component of the neural circuitry underlying emotional consequences of drug reward. Oxytocin, on the other hand, has an effect on learning and memory opposite to that of vasopressin. Previous studies have shown that oxytocin caused a decrease in heroin self-administration, as well as attenuated the appearance of cocaine-induced hyperactivity and stereotyped behaviour. Therefore, we adopted a reinstatement conditioned place preference model to investigate whether a V1b antagonist or oxytocin treatment would cause a decrease in methamphetamine seeking behaviour. Behavioural findings indicated that methamphetamine induced a change in the place preference in the majority of our animals. This change in preference was not seen after vasopressin administration in the extinction phase. On the other hand, the change in place preference was enhanced during the reinstatement phase in the animals treated with oxytocin. Striatal dopamine levels were determined, as methamphetamine is known to increase dopamine transmission in this area. Results showed that rats that received both methamphetamine and oxytocin had significantly higher striatal dopamine than those that received oxytocin alone. Western blot analysis for hippocampal cyclic AMP response element binding protein (CREB) was also conducted as a possible indicator of glutamatergic NMDA receptor activity, a pathway that is important for learning and memory. The Western blot analysis showed no changes in hippocampal pCREB expression. Overall our data led us to conclude that methamphetamine treatment can change place preference behaviour in rats and that this change may be partially restored by vasopressin antagonism, but exaggerated by oxytocin

Structure-Activity Relationship Studies of Synthetic Cathinones and Related Agents

Synthetic cathinones and related agents represent an international drug abuse problem, and at the same time an important class of clinically useful compounds. Structure-activity relationship studies are needed to elucidate molecular features underlying the pharmacology of these agents. Illicit methcathinone (i.e., MCAT), the prototype of the synthetic cathinone class, exists as a racemic mixture. Though the differences in potency and target selectivity between the positional and optical isomers of synthetic cathinones and related agents have been demonstrated to have important implications for abuse and therapeutic potential, the two MCAT isomers have never been directly compared at their molecular targets: the monoamine transporters (MATs). Additionally, previous studies have found that the carbonyl oxygen atom can be replaced with a methoxy group, but this results in two chiral centers (i.e., four possible optical isomers for synthesis and evaluation). Here, the individual isomers of MCAT, their racemate, and achiral MCAT analogs were prepared where necessary, and examined in vitro and in silico at the MATs. All agents were active as substrates, with a rank order of potency suggesting that α-position chirality, in either configuration, is favored but not required, with the S(-) configuration slightly preferred. Either chiral center removal approach resulted in a reduction in potency, suggesting both favorable interactions with the α-methyl, and limited bulk tolerance. To further investigate this possibility, docking studies were conducted using homology models of the MATs. Common binding modes were identified that were similar to the binding mode of S(+)amphetamine co-crystallized at drosophila DAT. Taken together, these studies supported our conclusions, as steric hindrance was observed in the α-methyl region of the proposed binding site for the R(+)MCAT isomer. Inclusion of the original synthetic cathinones among Schedule I controlled substances has driven the clandestine development of a second generation of agents, resulting in an array of new synthetic cathinones diverse in structure and effect.Pyrrolidinophenones are a major constituent of second-generation bath salts. Little is known about their structure-activity relationships. Here, we have synthesized and examined a series of aryl-substituted pyrrolidinophenone analogs, as well as an achiral pyrrolidinophenone analog, utilizing novel synthetic chemistry and an innovative cell-based epifluorescence Ca2+ imaging technique. Herein, we evaluated the neurochemical properties of these novel compounds at the dopamine transporter (DAT), considered to exert a major role in actions of drugs of abuse. For future structure-activity relationship studies, additional analogs of synthetic cathinone-related agents were produced using novel synthetic approaches, including analogs and isomers of known amphetamine drugs of abuse. Finally, though much has been learned about the role of the dopamine and serotonin transporters in the mechanisms of action of synthetic cathinones, the role of the norepinephrine transporter is poorly understood. Homology models of the human norephinephrine transporter were built and docking studies conducted to inform the study of MAT ligand selectivity, activity, and binding. In conclusion, these studies represent progress towards the establishment of comprehensive structure-activity relationships for synthetic cathinones and related agents. Particular emphasis was placed on the SAR of the phenylalkylamine α-carbon in the synthetic cathinone context, and the role of the norepinephrine transporter in their activity

Neuroprotection or neurotoxicity of illicit drugs on Parkinson’s disease

Parkinson’s Disease (PD) is currently the most rapid growing neurodegenerative disease and over the past generation, its global burden has more than doubled. The onset of PD can arise due to environmental, sporadic or genetic factors. Nevertheless, most PD cases have an unknown etiology. Chemicals, such as the anthropogenic pollutant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and amphetamine-type stimulants, have been associated with the onset of PD. Conversely, cannabinoids have been associated with the treatment of the symptoms’. PD and medical cannabis is currently under the spotlight, and research to find its benefits on PD is on-going worldwide. However, the described clinical applications and safety of pharmacotherapy with cannabis products are yet to be fully supported by scientific evidence. Furthermore, the novel psychoactive substances are currently a popular alternative to classical drugs of abuse, representing an unknown health hazard for young adults who may develop PD later in their lifetime. This review addresses the neurotoxic and neuroprotective impact of illicit substance consumption in PD, presenting clinical evidence and molecular and cellular mechanisms of this association. This research area is utterly important for contemporary society since illicit drugs’ legalization is under discussion which may have consequences both for the onset of PD and for the treatment of its symptoms.publishersversionpublishe

Voluntary Oral Methamphetamine Reveals Susceptibilities to Spatial Memory Deficits, Decreased Dopamine Marker Expression and Increased Neuroinflammation in the Hippocampus of Male and Female Mice

Methamphetamine is an addictive illicit psychostimulant that produces lasting neurochemical and behavioral changes. The mechanisms underlying these deficits have been characterized in animal models using extremely high doses. Currently, better translational models are needed to understand the onset and progression of these deficits that more accurately reflect the gradual and voluntary dosing parameters as chosen by an abuser. To that end, a new model of methamphetamine administration, labeled Voluntary Oral Methamphetamine Administration (VOMA), offers a means to examine the progression of neurotoxicity, behavioral deficits, and the addiction process through a voluntary consumption framework. Female populations show consistent vulnerabilities to methamphetamine, including greater severity of abuse, and greater shifts in psychological health. Females also show increased neurochemical susceptibilities during abstinence from methamphetamine, exhibiting increased grey-matter loss compared to controls. The mechanisms underlying these female-specific susceptibilities to methamphetamine are unknown. The overall GOAL of these studies was to establish a voluntary methamphetamine administration model in mice that recapitulates the cognitive and neurochemical deficits shown with previous models to further our understanding of the long-term susceptibilities of at-risk populations, including adolescent and female subjects. Rodents can exhibit drug-preference and drug-seeking behaviors, and methamphetamine challenges can reproduce the behavioral and neurochemical deficits that human addicts show. However, it is unclear if mice would voluntarily consume methamphetamine, and what effects this administration design would produce in this mice. Thus, the studies presented in this dissertation characterized the utility of the VOMA model to produce 1. naturalistic methamphetamine consumption 2. behavioral deficits and 3. neurochemical changes. This was done in an effort to understand the 4. mechanisms underlying adolescent- and female-specific vulnerabilities to the drug. To achieve our GOAL, we carried out three (3) specific aims: Specific Aim 1: Determine the utility of Voluntary Oral Methamphetamine Administration (VOMA) to produce behavioral and neurochemical deficits as seen in previous models [Chapter 2] In modeling MA abuse with rodents, researchers have developed paradigms that inject neurotoxic or binge doses in mice that are 10 times higher than the lower limits we have characterized in our models 1 (reviewed in2). Previous work in this line of research has found that two (2) 30mg/kg MA doses can acutely increase spatial working-memory performance but also increase spatial working-memory errors in the long-term. These effects were correlated to decreased DA and synaptic plasticity maker expression in the hippocampus 1. These prior studies have contributed significantly to our understanding of the mechanisms underlying MA toxicity 2, but offered very little in understanding the voluntary nature of methamphetamine administration. In order to characterize the utility of VOMA in producing MA consumption that produced cognitive and neurochemical deficits, we combined a spatial cognition design with a drug administration design as follows: mice were randomly assigned to either a water/control group or MA for 28 consecutive days. To carry out voluntary oral MA administration (VOMA) in mice, MA was mixed into a palatable sweetened oatmeal flake that mice were drawn to and ingested orally. Mice were allowed to consume MA throughout a 3-hour administration period, within 15 min intervals. Following 28-days of VOMA, mice were sacrificed, and tissues were collected. We found that VOMA: (1) Decreased working-memory and reference-memory performance of male mice on the radial arm maze. These behavioral deficits were observed after the 28-day drug administration period over a 2-week abstinence period. (2) Increased neurotoxicity in the hippocampus, as observed through lower dopamine marker expression, increased neuroinflammation, and lower synaptic-plasticity marker expression. Overall, these results indicate that VOMA can produce the behavioral and the neurochemical deficits observed in previous animal models as well as in human methamphetamine addicts. Additionally, that the molecular deficits were observed in the hippocampus highlights the utility of the model to easily characterize correlative cognitive behaviors and the underlying molecular shifts. Specific Aim 2: Characterize the role of abstinence in perpetuating methamphetamine-induced deficits using VOMA [Chapter 3] MA abuse can produce long-term cognitive impairments in abstinent individuals3-5 but other studies have shown that long periods of abstinence can improve the recovery of decision making-skills and emotional symptoms6. This may help individuals to avert relapse and yet, other reports indicate that relapse can occur after abstinence7, as a result of exposure to specific environmental cues8. The neurochemical pathways affected by abstinence from MA are also unclear. An understanding of the progression of behavioral and neurochemical changes produced by MA abuse and by abstinence would provide pharmacological targets to aid in recovery from addiction. In order to characterize the role of abstinence in producing MA-induced behavioral and molecular deficits, we used an acute VOMA design to do the following: put adolescent mice through cognitive assessments directly after 14 days of MA exposure and after a prolonged abstinence period. Tissue was collected directly after VOMA and after a 4-week abstinence period. We found that VOMA: (1) Produced a transient sensitization to MA as seen through behavior analyses in the drug-context (2) Produced an acute spatial working-memory deficit on the RAM directly after VOMA We found that abstinence: (1) Did not produce long-term working-memory, reference learning, nor retention deficits on the RAM (2) Increased expression of neuroinflammatory markers in the hippocampus (3) Modulated expression of monoamine proteins in the hippocampus Overall, these results indicate that abstinence from VOMA acutely affects behavioral performance that is ameliorated by abstinence. Further, abstinence produces neurochemical changes not observed directly following VOMA. This demonstrates that even acute MA exposure is sufficient to produce molecular changes in the brain despite not manifesting in behavior. This highlights the susceptibility of the adolescent brain to acute MA exposure and provides new avenues for pharmacological studies aimed at preventing MA-induced deficits. Specific Aim 3: Characterize the sex-differences in behavior and neurochemistry following escalating dose of methamphetamine using VOMA [Chapter 4] Previous work has shown that females exhibit susceptibilities to psychostimulant-addiction 9-12. It has been reported that methamphetamine use in female populations can be attributed to factors including weight loss, desire for increased energy and work output, and decreased exhaustion 13-14. Data on drug-rehabilitation admissions show that young female participants are admitted at higher rates compared to males 15. One hypothesis for sex differences in psychostimulant addiction highlights estrogen’s facilitation of neuronal and behavioral development of drug addiction processes in the brain. 16-18. However, this idea remains untested. Additionally, previous work has shown that escalating doses of methamphetamine have intrinsic neuroprotective qualities that protect the brain and behavior from a chronic administration of the drug. The nature and source of this neuroprotection is unclear, but previous work has shown that this phenomenon occurs in binge injection models, 19-20, associated with decreases in methamphetamine binding to DAT and decreases in the resulting DA availability in the synapse. However, the underlying mechanisms that produce this change in DA sensitivity remain unknown. To test how female subjects respond differentially to VOMA, we modified our administration design to include a 10-day escalation period, wherein mice would receive gradually escalating doses of and access to methamphetamine prior to receiving the maximum access and dose. We hypothesized that that this administration design would produce the maximal voluntary consumption over a shorter (18-day) period and produce the maximal behavioral and molecular deficits that could be observed. We found that Escalation-VOMA: (1) Decreased working-memory of female mice on the radial arm maze shortly after the conclusion of VOMA. This deficit was not observed in male mice that were placed into VOMA. (2) Discrete shifts in neuroprotective signaling (D1, ERα and Akt/GSK3β pathway) in the hippocampus and nucleus accumbens of female mice after a 2-week abstinence period. Male mice that underwent VOMA did not exhibit any molecular changes. Overall, this study showed that through VOMA, and with the aid of an escalating-dose design, we are able to observe sex-differences in the behavioral and neurochemical changes that methamphetamine can produce. Interestingly, we also observed a previously reported neuroprotective effect of escalating doses in male subjects, but not in females. Our molecular investigations will provide future direction in basic research and clinical endeavors to target methamphetamine addiction. Conclusion: The novel VOMA design has provided a more naturalistic approach to investigating the behavioral and molecular deficits produce by methamphetamine and abstinence during adolescence. With this model, we have successfully characterized longer-term susceptibilities in mice than previous studies have shown. Furthermore, it has provided new insights into the sex-differences surrounding meth-abuse, including the role of neuroprotective pathway signaling as markers for susceptibilities/resilience to methamphetamine abus

Psychomotor Symptoms in Chronic Cocaine Users: An Interpretative Model

According to the latest estimates, there are around 24.6 million cocaine users worldwide, and it is estimated that around a quarter of the population worldwide has used cocaine at some point in their lifetime. It follows that such widespread consumption represents a major risk for public health. Long\u2010term use of cocaine, in addition to being related to many cerebral and cardiovascular diseases, is increasingly associated with a higher incidence of psychomotor symptoms and neurodegenerative disorders. In recent years, numerous studies have shown an increased risk of antipsychotic\u2010induced extrapyramidal symptoms (EPSs) in patients with psychotic spectrum disorders comorbid with psychostimulant misuse, particularly of cocaine. In the present paper, we describe the case of a young patient on his first entry into a psychiatric setting with previous cocaine misuse who rapidly presented psychomotor symptoms and was poorly responsive to symptomatic therapy consisting of benzodiazepines and anticholinergics, in relation to the introduction of various antipsychotics (first, second, and third generation). Furthermore, we propose neurobiological mechanisms underlying the hypothesized increased vulnerability to psychomotor symptoms in chronic cocaine abusers. Specifically, we supposed that the chronic administration of cocaine produces important neurobiological changes, causing a complex dysregulation of various neurotransmitter systems, mainly affecting subcortical structures and the dopaminergic and glutamatergic pathways. We believe that a better understanding of these neurochemical and neurobiological processes could have useful clinical and therapeutic implications by providing important indications to increase the risk\u2013benefit ratio in pharmacological choice in patients with psychotic spectrum disorders comorbid with a substance use disorder