Innovation and adaptation: The rise of a fentanyl smoking culture in San Francisco.

BACKGROUND: Illicitly manufactured fentanyls and stimulants are implicated in the escalating US mortality from drug overdose. San Francisco, California (SF) has seen declining fentanyl injection while smoking has increased. Beliefs and behaviors surrounding this development are not well understood. METHODS: The study used rapid ethnography to explore fentanyl and methamphetamine use in SF. The team conducted semi-structured interviews (n = 34) with participants recruited from syringe service programs. Video-recorded smoking sequences (n = 12), photography and daily field notes supplemented interview data. RESULTS: Difficulty injecting and fear of overdose motivated transitions from injecting to smoking. Fentanyl was extremely cheap-$10/gram-with variability in quality. Foil was the most commonly used smoking material but glass bubbles, bongs and dabbing devices were also popular. No reliable visible methods for determining fentanyl quality existed, however, participants could gauge potency upon inhalation, and developed techniques to regulate dosage. Several participants reported at least hourly use, some reporting one or more grams of daily fentanyl consumption. Smoking was also very social, with people sharing equipment, drugs and information. Participants raised concerns about hygiene and overdose risk to others arising from shared equipment. Reportedly potent fentanyl 'residue' accumulated on smoking materials and was commonly shared/traded/stolen or consumed accidentally with diverse preferences for its use. CONCLUSION: Our data highlight fentanyl residue as a new overdose risk with potential mismatch between the potency of the residual drug and the recipient's tolerance. Further, large doses of fentanyl are being consumed (estimated at approximately 50 mg of pure fentanyl/day). Smoking fentanyl has potential health benefits over injecting and may be protective against overdose, but substantial uncertainty exists. However, SF overdose mortality hit a record high in 2023. Recommendations to reduce fentanyl smoking overdose risks through pacing, greater awareness of dosages consumed and checking tolerance of residue recipients are potentially viable interventions deserving further exploration.

Changes in injecting versus smoking heroin, fentanyl, and methamphetamine among people who inject drugs in San Diego, California, 2020-2023.

BACKGROUND: Amidst an increasingly toxic drug supply in North America, people who inject drugs may be transitioning to smoking them. We aimed to assess changes in injecting and smoking opioids and methamphetamine among a cohort of people who inject drugs from San Diego, California. METHODS: Over five six-month periods spanning October 2020-April 2023, we assessed prevalence of injecting and smoking opioids or methamphetamine and whether participants used these drugs more frequently by smoking than injecting. Multivariable Poisson regression via generalized estimating equations was used to examine time trends. RESULTS: Of 362 participants, median age was 40 years; a minority were female (29%), Hispanic/Latinx/Mexican (45%), and housed (33%). Among this cohort, of whom 100% injected (and 84% injected and smoked) in period one (October 2020-April 2021), by period five (November 2022-April 2023), 34% only smoked, 59% injected and smoked, and 7% only injected. By period five, the adjusted relative risk (aRR) of injecting opioids was 0.41 (95% Confidence Interval [CI]: 0.33, 0.51) and the aRR for injecting methamphetamine was 0.50 (95% CI: 0.39, 0.63) compared to period one. Risks for smoking fentanyl rose significantly during period three (aRR=1.44, 95% CI: 1.06, 1.94), four (aRR=1.65, 95% CI: 1.24, 2.20) and five (aRR=1.90, 95% CI: 1.43, 2.53) compared to period one. Risks for smoking heroin and methamphetamine more frequently than injecting these drugs increased across all periods. CONCLUSIONS: Opioid and methamphetamine injection declined precipitously, with notable increases in smoking these drugs. Research is needed to understand the health consequences of these trends.

Co-administration of naloxone and dexmedetomidine to simultaneously reverse acute effects of fentanyl and methamphetamine in rats.

BACKGROUND: The incidence of combination methamphetamine (METH)-opioid overdose has substantially increased in recent years. While agitation is uncommon after the naloxone (NLX) reversal of opioids, it is a major clinical concern in acute METH intoxication and can be physiologically antagonized by opioid-induced sedation. This study aimed to perform initial preclinical analysis of the safety and efficacy of dexmedetomidine (DEXMED) co-administered with NLX to attenuate METH-induced locomotor activity, as a rat model of agitation, after the reversal of fentanyl (FENT)-induced sedation. METHODS: Male Sprague Dawley rats were administered subcutaneous (SC) 0.1mg/kg FENT ± 1mg/kg METH. Fifteen min later, SC 0.1mg/kg NLX ± an increasing (0, 0.032, 0.056, and 0.1mg/kg) DEXMED dose was administered prior to the measurement of locomotor activity. After a washout period, the FENT ± METH and NLX ± DEXMED administration with the highest dose of DEXMED was administered for measurement of blood oxygen saturation and heart rate. RESULTS: After the NLX reversal of FENT-induced sedation, adjunct DEXMED substantially and significantly reduced METH-induced locomotor activity (p<0.05) at all doses tested. While the addition of DEXMED did not significantly reduce blood oxygenation in METH treated rats, it did so in the absence of METH. Also, DEXMED significantly reduced heart rate compared to non-DEXMED treated groups and resulted in further significant reductions in the animals not exposed to METH (p<0.05). CONCLUSIONS: These data provide preclinical evidence that DEXMED may be a safe and effective chemical restraint for METH-induced agitation after NLX opioid reversal.

Methamphetamine increases risky choice in rats, but only when magnitude and probability of reinforcement are manipulated within a session.

Risky choice is associated with maladaptive behaviors, particularly substance use disorders. Current animal models of risky choice are often confounded by other constructs like behavioral flexibility and suboptimal choice. The purpose of the current experiment was to determine if the psychostimulant methamphetamine, a drug whose popularity has increased in recent years, increases risky choice in an equivalent expected value (EEV) task. In the EEV task, rats are given a choice between two reinforcer alternatives that differ in magnitude and probability of delivery, but have equivalent expected value. Forty-eight Sprague Dawley rats were tested in three versions of the EEV task. In the first version of the EEV task, both reinforcer magnitude and probability were adjusted across blocks of trials for both alternatives. In the second and the third versions of the EEV task, reinforcer magnitude was held constant across each block of trials (either 1 vs. 2 pellets or 4 vs. 5 pellets). We found that male rats preferred the "riskier" option, except when reinforcer magnitudes were held constant at 4 and 5 pellets across each block of trials. Methamphetamine (0.5 mg/kg) increased preference for the risky option in both males and females, but only when both reinforcer magnitude and probability were manipulated across blocks of trials for each alternative. The current results demonstrate that both magnitude of reinforcement and probability of reinforcement interact to influence risky choice. Overall, this study provides additional support for using reinforcers with expected value to measure risky choice.

SMART Family and Friends: Feasibility and outcomes of a video-conference delivered intervention for families impacted by another's methamphetamine use.

INTRODUCTION: Families affected by another's substance use, including methamphetamine, experience harms to their mental and physical health. Yet, research has paid little attention to support and service needs of this population. This pilot study examines the feasibility and outcomes of SMART Family and Friends, a video-conference-delivered mutual-support group targeting families affected by another's methamphetamine use. METHODS: Recruitment for this study occurred between March-October 2021 via the SMART Recovery Australia website. Participants were English-speaking Australian residents, ≥18 years, affected by another's methamphetamine use, interested in participating in a manualised eight-module group delivered via video-conferencing. Feasibility was evaluated by attendance rates, participant satisfaction, fidelity ratings, and semi-structured interviews. Measures of distress, quality of life, and family functioning assessed outcomes at baseline and one-month post-treatment conclusion. RESULTS: Forty-three participants commenced SMART Family and Friends groups. 84 % (n = 36) completed ≥4 modules, 67 % (n = 29) completed ≥6, and 42 % (n = 18) completed all 8 modules. Participant satisfaction (M = 4.32, SD = 0.66, out of 5) and facilitator fidelity (>94 % for all modules) were high. A within-group analysis, without comparison condition demonstrated significant improvements in psychological distress (d = 0.38), family impact (d = 0.64), family strain symptoms (d = 0.48), and total family burden (d = 0.69) post-treatment. Qualitative findings illustrated the benefits and challenges of the video-conference-delivered group, as well as recommendations for improvement. CONCLUSIONS: Results provide initial support for the feasibility and positive outcomes of the SMART Family and Friends program. These findings demonstrate the successful provision of a mutual-support group for affected families delivered via video-conferencing, and merit further sufficiently powered randomised-control-trials to evaluate efficacy.

Participant experiences in a pilot study for methamphetamine withdrawal treatment: Implications for retention.

INTRODUCTION: There is little knowledge of the perspectives of people who use methamphetamine and have participated in clinical trials, and none for interventions not intended to address abstinence. A better understanding of these experiences could lead to more patient centred clinical trial design. This study seeks to understand the experiences of people who completed a clinical trial of lisdexamfetamine for the treatment of acute methamphetamine withdrawal. METHODS: Thematic analysis of open-ended, semi-structured interviews with eight people who participated in an inpatient clinical trial of lisdexamfetamine for acute methamphetamine withdrawal. Interviews were conducted between days 3 and 6 of admission to an inner-city Sydney hospital. RESULTS: Participants described how research procedures, the research setting, and the investigational product affected their experiences while enrolled in a clinical trial. Of particular importance to participants were transparent and low burden trial procedures, a welcoming trial environment, trusting relationships and effective communication, which were linked with the participants' subsequent decision to remain enrolled in the trial. DISCUSSION: The experiences of participants in this clinical trial can be distilled into four meta-themes: agency, caring-trust, safety, and communication. Participants spontaneously linked these experiences with a capacity to remain enrolled in the study. By considering the experiences of trial participants in clinical trial design, researchers can improve the experiences of future trial participants and facilitate their choice to remain enrolled in clinical trials.

PrEP Uptake and Methamphetamine Use Patterns in a 4-Year U.S. National Prospective Cohort Study of Sexual and Gender Minority People, 2017-2022.

Methamphetamine use is on the rise among sexual and gender minority people who have sex with men (SGMSM), escalating their HIV risk. Despite pre-exposure prophylaxis (PrEP) being an effective biomedical HIV prevention tool, its uptake in relation to methamphetamine use patterns in SGMSM has not been studied. In a U.S. cohort study from 2017 to 2022, 6,253 HIV-negative SGMSM indicated for but not using PrEP were followed for four years. Methamphetamine use was categorized (i.e., newly initiated, persistently used, never used, used but quit), and PrEP uptake assessed using generalized estimating equation (GEE), adjusted for attrition. Participants had a median age of 29, with 51.9% White, 11.1% Black, 24.5% Latinx, and 12.5% other races/ethnicities. Over the four years, PrEP use increased from 16.3 to 27.2%. GEE models identified risk factors including housing instability and food insecurity. In contrast, older age, health insurance, clinical indications, and prior PrEP use increased uptake. Notably, Latinx participants were more likely to use PrEP than Whites. Regarding methamphetamine use, those who newly initiated it were more likely to use PrEP compared to non-users. However, those who quit methamphetamine and those who persistently used it had PrEP usage rates comparable to those of non-users. Though PrEP uptake increased, it remained low in SGMSM. Methamphetamine use was associated with PrEP uptake. Healthcare providers should assess methamphetamine use for harm reduction. Prioritizing younger, uninsured SGMSM and addressing basic needs can enhance PrEP uptake and reduce HIV vulnerabilities.

Neural complexity is increased after low doses of LSD, but not moderate to high doses of oral THC or methamphetamine.

Neural complexity correlates with one's level of consciousness. During coma, anesthesia, and sleep, complexity is reduced. During altered states, including after lysergic acid diethylamide (LSD), complexity is increased. In the present analysis, we examined whether low doses of LSD (13 and 26 µg) were sufficient to increase neural complexity in the absence of altered states of consciousness. In addition, neural complexity was assessed after doses of two other drugs that significantly altered consciousness and mood: delta-9-tetrahydrocannabinol (THC; 7.5 and 15 mg) and methamphetamine (MA; 10 and 20 mg). In three separate studies (N = 73; 21, LSD; 23, THC; 29, MA), healthy volunteers received placebo or drug in a within-subjects design over three laboratory visits. During anticipated peak drug effects, resting state electroencephalography (EEG) recorded Limpel-Ziv complexity and spectral power. LSD, but not THC or MA, dose-dependently increased neural complexity. LSD also reduced delta and theta power. THC reduced, and MA increased, alpha power, primarily in frontal regions. Neural complexity was not associated with any subjective drug effect; however, LSD-induced reductions in delta and theta were associated with elation, and THC-induced reductions in alpha were associated with altered states. These data inform relationships between neural complexity, spectral power, and subjective states, demonstrating that increased neural complexity is not necessary or sufficient for altered states of consciousness. Future studies should address whether greater complexity after low doses of LSD is related to cognitive, behavioral, or therapeutic outcomes, and further examine the role of alpha desynchronization in mediating altered states of consciousness.

The motives and methods of methamphetamine and 'heroin' co-use in West Virginia.

BACKGROUND: Opioid and methamphetamine co-use is increasing across the USA with overdoses involving these drugs also rising. West Virginia (WV) has led the US in opioid overdose death rates since at least 2013 and rising co-use of methamphetamine with opioids has played a greater role in deaths over the last 5 years. METHODS: This study used rapid ethnography to examine methods and motivations behind opioids and methamphetamine co-use from the viewpoint of their consumers. Participants (n = 30) were people who injected heroin/fentanyl also using methamphetamine who participated in semi-structured interviews. RESULTS: We found multiple methods of co-using opioids and methamphetamine, whether alternately or simultaneously and in varying order. Most prioritized opioids, with motives for using methamphetamine forming three thematic categories: 'intrinsic use', encompassing both inherent pleasure of combined use greater than using both drugs separately or for self-medication of particular conditions; 'opioid assisting use' in which methamphetamine helped people manage their existing heroin/fentanyl use; and 'reluctant or indifferent use' for social participation, reflecting methamphetamine's low cost and easy availability. CONCLUSIONS: Methamphetamine serves multiple functions among people using opioids in WV. Beliefs persist that methamphetamine can play a role in preventing and reversing opioid overdose, including some arguments for sequential use being protective of overdose. 'Reluctant' uptake attests to methamphetamine's social use and the influence of supply. The impact on overdose risk of the many varied co-use patterns needs further investigation.

Modeling methamphetamine use disorder and relapse in animals: short- and long-term epigenetic, transcriptional., and biochemical consequences in the rat brain.

Methamphetamine use disorder (MUD) is a neuropsychiatric disorder characterized by binge drug taking episodes, intervals of abstinence, and relapses to drug use even during treatment. MUD has been modeled in rodents and investigators are attempting to identify its molecular bases. Preclinical experiments have shown that different schedules of methamphetamine self-administration can cause diverse transcriptional changes in the dorsal striatum of Sprague-Dawley rats. In the present review, we present data on differentially expressed genes (DEGs) identified in the rat striatum following methamphetamine intake. These include genes involved in transcription regulation, potassium channel function, and neuroinflammation. We then use the striatal data to discuss the potential significance of the molecular changes induced by methamphetamine by reviewing concordant or discordant data from the literature. This review identified potential molecular targets for pharmacological interventions. Nevertheless, there is a need for more research on methamphetamine-induced transcriptional consequences in various brain regions. These data should provide a more detailed neuroanatomical map of methamphetamine-induced changes and should better inform therapeutic interventions against MUD.

Transmission Of Tuberculosis Among illicit drug use Linkages (TOTAL): A cross-sectional observational study protocol using respondent driven sampling.

People who use illicit drugs (PWUDs) have been identified as a key at-risk group for tuberculosis (TB). Examination of illicit drug use networks has potential to assess the risk of TB exposure and disease progression. Research also is needed to assess mechanisms for accelerated TB transmission in this population. This study aims to 1) assess the rate of TB exposure, risk of disease progression, and disease burden among PWUD; 2) estimate the proportion of active TB cases resulting from recent transmission within this network; and 3) evaluate whether PWUD with TB disease have physiologic characteristics associated with more efficient TB transmission. Our cross-sectional, observational study aims to assess TB transmission through illicit drug use networks, focusing on methamphetamine and Mandrax (methaqualone) use, in a high TB burden setting and identify mechanisms underlying accelerated transmission. We will recruit and enroll 750 PWUD (living with and without HIV) through respondent driven sampling in Worcester, South Africa. Drug use will be measured through self-report and biological measures, with sputum specimens collected to identify TB disease by Xpert Ultra (Cepheid) and mycobacterial culture. We will co-enroll those with microbiologic evidence of TB disease in Aim 2 for molecular and social network study. Whole genome sequencing of Mycobacteria tuberculosis (Mtb) specimens and social contact surveys will be done for those diagnosed with TB. For Aim 3, aerosolized Mtb will be compared in individuals with newly diagnosed TB who do and do not smoke illicit drug. Knowledge from this study will provide the basis for a strategy to interrupt TB transmission in PWUD and provide insight into how this fuels overall community transmission. Results have potential for informing interventions to reduce TB spread applicable to high TB and HIV burden settings. Trial registration: Clinicaltrials.gov Registration Number: NCT041515602. Date of Registration: 5 November 2019.

The effects of alcohol drinking on subsequent methamphetamine self-administration and relapse in adolescent female rats.

Alcohol and Methamphetamine (Meth) are widely abused drugs that are frequently co-abused, though this pattern of polysubstance abuse is rarely studied. Alcohol use during adolescence is associated with subsequent Meth dependence in humans and female adolescents may be more vulnerable than males to serial alcohol and Meth use. However, it is unknown if prior alcohol drinking impacts subsequent Meth-taking in female rats. This study uses a novel method of serial voluntary alcohol drinking and Meth self-administration in female adolescent Sprague Dawley rats (n = 35) to model human patterns of co-abuse. Rats demonstrated a steady time-based increase in alcohol preference versus water, starting at 33.3 ± 3.4% on day 1-48.0 ± 3.6% by the final day of EtOH, with a peak EtOH preference of 49.7 ± 3.7% on day 17 of the drinking paradigm (P < 0.001, one-way repeated measures ANOVA). All rats rapidly acquired Meth self-administration, demonstrating a 4.6 ± 1.4 fold increase in active presses for Meth and a 5.2 ± 1.8 fold increase in Meth intake (mg/kg) within 7 days, and maintained high levels of Meth intake throughout 21 days of self-administration. Prior alcohol drinking did not alter the increase in Meth self-administration compared to alcohol naïve control rats. However, after 7 days of Meth abstinence, a history of alcohol drinking reduced cue-primed reinstatement of Meth seeking. These findings demonstrate that prior alcohol consumption does not alter overall Meth self-administration but does persistently reduce cue-primed Meth seeking after prolonged alcohol abstinence.

Dopamine sensitization by methamphetamine treatment prior to instrumental training delays the transition into habit in female rats.

Early in instrumental learning, behavior is goal-directed and sensitive to changes in the value of the instrumental outcome. With sufficient repetition, responding becomes insensitive to changes in outcome value, or habitual. We have previously found that females transition into habit over a distinct range of training from 120 to 160 reinforced responses. This low level of instrumental training is markedly less than what has been shown to support habitual responding in male rats. To begin to investigate the early development of habit in females, we conducted a series of experiments in which we pretreated female rats with methamphetamine (METH) with the aim of sensitizing central dopamine, a major modulator of striatal function, prior to instrumental nose-poke training at the beginning and at the endpoint of the transition range in females. Following training, we tested for sensitivity to reinforcer devaluation (RD), which was conducted by repeatedly pairing reinforcers previously earned during training with lithium chloride (LiCl)-induced illness. As a counterpoint, a series of similar experiments was conducted separately in male rats. Additionally, in order to ascertain the validity of using nose-poke as an instrumental response, we compared sensitivity to devaluation between the Pavlovian approach towards the food magazine and the nose-poke response. In females, Vehicle groups responded in a habitual manner at both training levels (120 and 160 reinforced responses), whereas METH groups remained sensitive to devaluation. This suggests that increasing central dopamine delays habit formation in female rats. In male rats, Vehicle groups demonstrated goal-directed responding following training with 120 and 320 reinforced responses, and marginally goal-directed responding,with 160. METH-pretreated males were sensitive to devaluation at the 120 and 160 training levels, however, following more extended training to 320 reinforced responses, METH-pretreated males responded in a habitual manner, indicating that increasing central dopamine can advance habit formation in male rats. Overall, these results suggest that METH pretreatment maintains goal-directed responding in female rats when they are typically transitioning to habitual control of instrumental behavior and can advance habit formation in male rats given sufficient instrumental training. In addition, we found differential RD sensitivity of the nose-poke response used during instrumental training compared to Pavlovian approach towards the food magazine, confirming that there is a distinction between these two behaviors and that nose-poking is a valid instrumental response.

Methamphetamine use in the United States: epidemiological update and implications for prevention, treatment, and harm reduction.

Recent attention has focused on the growing role of psychostimulants, such as methamphetamine in overdose deaths. Methamphetamine is an addictive and potent stimulant, and its use is associated with a range of physical and mental health harms, overdose, and mortality. Adding to the complexity of this resurgent methamphetamine threat is the reality that the increases in methamphetamine availability and harms are occurring in the midst of and intertwined with the ongoing opioid overdose crisis. Opioid involvement in psychostimulant-involved overdose deaths increased from 34.5% of overdose deaths in 2010 to 53.5% in 2019-an increase of more than 50%. This latest evolution of the nation's overdose epidemic poses novel challenges for prevention, treatment, and harm reduction. This narrative review synthesizes what is known about changing patterns of methamphetamine use with and without opioids in the United States, other characteristics associated with methamphetamine use, the contributions of the changing illicit drug supply to use patterns and overdose risk, motivations for couse of methamphetamine and opioids, and awareness of exposure to opioids via the illicit methamphetamine supply. Finally, the review summarizes illustrative community and health system strategies and research opportunities to advance prevention, treatment, and harm reduction policies, programs, and practices.

Roflumilast treatment during forced abstinence reduces relapse to methamphetamine seeking and taking.

Methamphetamine (METH) is a psychostimulant with high abuse potential. Currently, there are no pharmacological treatments specific for METH abuse or stimulant use disorder generally. Although phosphodiesterase inhibitors have shown some promise, current animal models have not examined their use in abstinence from stimulant abuse. We employed a METH self-administration model in the rat followed by a forced abstinence period during which roflumilast, a phosphodiesterase 4 inhibitor, was administered. A detailed behavioral analysis of chronic treatment with roflumilast during 7 days of forced abstinence showed that roflumilast reduced METH seeking and METH taking upon subsequent relapse test. Roflumilast treatment during 7 days of forced abstinence did not affect sucrose seeking and sucrose taking behaviors. These data suggest that roflumilast may be a treatment for METH use disorder that is effective when administered only during abstinence.

Repeated oxytocin treatment during abstinence inhibited context- or restraint stress-induced reinstatement of methamphetamine-conditioned place preference and promoted adult hippocampal neurogenesis in mice.

Propensity to relapse, even after long-term abstinence, is a crucial feature of methamphetamine (METH) abuse. We and other laboratories have reported that acute treatment of oxytocin (OXT), a hormone and neuropeptide, could inhibit reinstatement of METH seeking in animal studies. However, the effects of repeated OXT treatment on METH reinstatement as well as underlying mechanisms are still unclear. In the present study, the effects of repeated OXT treatment during abstinence on context- or restraint stress-induced reinstatement were investigated using the mice conditioned place preference (CPP) paradigm. After three intermittent injections of METH (2 mg/kg, i.p.) to induce CPP, mice received a daily bilateral intra-hippocampus injection of OXT (0.625, 1.25 or 2.5 µg) for 8 consecutive days before the context- or restraint stress-induced reinstatement test. Meanwhile, adult hippocampal neurogenesis (AHN) level was detected using immunostaining. To further clarify the role of AHN underlying OXT's effects on METH-CPP reinstatement, temozolomide (TMZ, 25 mg/kg, i.p.) was employed to deplete AHN prior to OXT treatment. The data showed that repeated OXT treatment (1.25 and 2.5 µg, intra-hippocampus) significantly inhibited both context- and restraint stress-induced METH-CPP reinstatement and concomitantly promoted AHN in a dose-dependent manner. Notably, TMZ pre-treatment markedly abolished all the above-mentioned effects of OXT, suggesting that AHN was closely involved in OXT's inhibition on reinstatement induced by both triggers. Taken together, the present study indicated that repeated OXT treatment during abstinence could inhibit both context- and restraint stress-induced METH-CPP reinstatement possibly by promoting AHN in mice, which provided a better understanding for OXT's beneficial effects on METH addiction.

The effect of mitragynine on extracellular activity of brain dopamine and its metabolites.

Kratom, derived from the plant Mitragyna speciosa (M. speciosa) Korth is a traditional psychoactive preparation widely used in Southeast Asia and increasingly in the rest of the world. Use and abuse of Kratom preparations can be attributed to mitragynine (MIT), the main psychoactive compound isolated from its leaves. While MIT may have beneficial effects as a recreational drug, for pain management, and for opiate withdrawal, it may have an addiction potential at higher doses. However, its action in the reward system of the brain is currently unknown. This study investigated how mitragynine (10 mg/kg, i.p.) affects extracellular activity of dopamine (DA) and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the prefrontal cortex (PFC), nucleus accumbens (NAc) and caudate putamen (CPu) of the brain, compared to morphine (MOR; 10 mg/kg, i.p.) and methamphetamine (METH; 10 mg/kg, i.p.). Using in-vivo microdialysis in freely moving rats, we found a significant increase of extracellular DA after MOR and METH, but not after MIT in all three brain regions. MIT led to a significant increase of DOPAC and/or HVA in these brain regions while MOR and METH had only moderate effects. These findings suggest a strong and prolonged effect of MIT on DA synthesis/metabolism, but not on extracellular DA activity, which may limit the addiction risk of MIT, in contrast to MOR and METH.

Effects of synthetic cathinone naphyrone in the conditioned place preference test - Evidence of its addictive potential.

Naphyrone, also known as NRG-1, is a novel psychoactive substance (NPS), a cathinone with stimulatory properties available on the grey/illicit drug market for almost a decade. It is structurally related to infamously known powerful stimulants with the pyrovalerone structure, such as alpha-pyrrolidinovalerophenone (α-PVP) or methylenedioxypyrovalerone (MDPV) that are labeled as a cheap replacement for cocaine and other stimulants. Despite the known addictive potential of α-PVP and MDPV, there are no studies directly evaluating naphyrone's addictive potential e.g., in conditioned place preference (CPP) test or using self-administration. Therefore, our study was designed to evaluate the addictive potential in a CPP test in male Wistar rats and compare its effect to another powerful stimulant with a high addictive potential - methamphetamine. Naphyrone increased time spent in the drug-paired compartment with 5 and 20 mg/kg s.c. being significant and 10 mg/kg s.c. reaching the threshold (p = 0.07); the effect was comparable to that of methamphetamine 1.5 mg/kg s.c. The lowest dose, naphyrone 1 mg/kg s.c., had no effect on CPP. Interestingly, no dose response effect was detected. Based on these data, we are able to conclude that naphyrone has an addictive potential and may possess a significant risk to users.

Alleviation of Methamphetamine Sensitization by Partially Lesioning Dopaminergic Terminals with 6-Hydroxydopamine in Nucleus Accumbens.

Amphetamine-type stimulants have become important and popular abused drugs worldwide. Methamphetamine (Meth) sensitization, characterized by a progressive increase in behavioral responses after repeated administration, has been reported in rodents and patients. This behavioral effect has been used as a laboratory model to study drug addiction and schizophrenia. The mesolimbic dopaminergic pathway plays a significant role in the development of Meth behavioral sensitization. Previous studies have reported that the ablation of nucleus accumbens (NAc) by electrolytic or thermal lesioning attenuates addictive behavior to opioids in animals. However, these studies were only conducted in opioid addictive rodents. Furthermore, these ablation procedures also damaged the non-dopaminergic neurons and fibers passing through the NAc. The purpose of this study was to examine the therapeutic effect of NAc lesioning by a selective dopaminergic toxin in Meth-sensitized animals. Adult mice received repeated administration of Meth for 7 days. Open-field locomotor activity and stereotype behavior were significantly increased after Meth treatment, suggesting behavior sensitization. A partial lesion of dopaminergic terminals was made through stereotaxic administration of dopaminergic toxin 6-hydroxydopamine (6-OHDA) to the NAc in the Meth -sensitized mice. Meth behavioral sensitization was significantly antagonized after the lesioning. Brain tissue was collected for qRT-PCR analysis. Repeated administration of Meth increased the expression of tyrosine hydroxylase (TH), BDNF, and Shati, a marker for Meth sensitization, in the NAc. Treatment with 6-OHDA significantly antagonized the upregulation of TH and Shati. Taken together, these data suggest that local administration of 6-OHDA mitigated Meth sensitization in chronic Meth-treated animals. Our data support a new surgical treatment strategy for Meth abuse.

Lactoferrin Protects against Methamphetamine Toxicity by Modulating Autophagy and Mitochondrial Status.

Lactoferrin (LF) was used at first as a vehicle to deliver non-soluble active compounds to the body, including the central nervous system (CNS). Nonetheless, it soon became evident that, apart from acting as a vehicle, LF itself owns active effects in the CNS. In the present study, the effects of LF are assessed both in baseline conditions, as well as to counteract methamphetamine (METH)-induced neurodegeneration by assessing cell viability, cell phenotype, mitochondrial status, and specific autophagy steps. In detail, cell integrity in baseline conditions and following METH administration was carried out by using H&E staining, Trypan blue, Fluoro Jade B, and WST-1. Western blot and immuno-fluorescence were used to assess the expression of the neurofilament marker ßIII-tubulin. Mitochondria were stained using Mito Tracker Red and Green and were further detailed and quantified by using transmission electron microscopy. Autophagy markers were analyzed through immuno-fluorescence and electron microscopy. LF counteracts METH-induced degeneration. In detail, LF significantly attenuates the amount of cell loss and mitochondrial alterations produced by METH; and mitigates the dissipation of autophagy-related proteins from the autophagy compartment, which is massively induced by METH. These findings indicate a protective role of LF in the molecular mechanisms of neurodegeneration.