Jacques D. Nguyen

Locomotor Stimulant and Rewarding Effects of Inhaling Methamphetamine, MDPV, and Mephedrone via Electronic Cigarette-Type Technology

Although inhaled exposure to drugs is a prevalent route of administration for human substance abusers, preclinical models that incorporate inhaled exposure to psychomotor stimulants are not commonly available. Using a novel method that incorporates electronic cigarette-type technology to facilitate inhalation, male Wistar rats were exposed to vaporized methamphetamine (MA), 3,4-methylenedioxypyrovalerone (MDPV), and mephedrone (4-methylmethcathinone) in propylene glycol vehicle using concentrations ranging from 12.5 to 200 mg/ml. Rats exhibited increases in spontaneous locomotor activity, measured by implanted radiotelemetry, following exposure to methamphetamine (12.5 and 100 mg/ml), MDPV (25, 50, and 100 mg/ml), and mephedrone (200 mg/ml). Locomotor effects were blocked by pretreatment with the dopamine D1-like receptor antagonist SCH23390 (10 μg/kg, intraperitoneal (i.p.)). MA and MDPV vapor inhalation also altered activity on a running wheel in a biphasic manner. An additional group of rats was trained on a discrete trial intracranial self-stimulation (ICSS) procedure interpreted to assess brain reward status. ICSS-trained rats that received vaporized MA, MDPV, or mephedrone exhibited a significant reduction in threshold of ICSS reward compared with vehicle. The effect of vapor inhalation of the stimulants was found comparable to the locomotor and ICSS threshold-reducing effects of i.p. injection of mephedrone (5.0 mg/kg), MA (0.5–1.0 mg/kg), or MDPV (0.5–1.0 mg/kg). These data provide robust validation of e-cigarette-type technology as a model for inhaled delivery of vaporized psychostimulants. Finally, these studies demonstrate the potential for human use of e-cigarettes to facilitate covert use of a range of psychoactive stimulants. Thus, these devices pose health risks beyond their intended application for the delivery of nicotine.

Escalation of intravenous self‐administration of methylone and mephedrone under extended access conditions

The recreational use of substituted cathinones continues to grow as a public health concern in the United States. Studies have shown that extended access to intravenous (i.v.) self‐administration of stimulants, such as cocaine and methamphetamine, results in escalation of drug intake relative to shorter access; however, little is known about the impact of extended access on self‐administration of entactogen class stimulants such as methylone and 4‐methylmethcathinone (mephedrone). Male Wistar rats were randomly assigned to short‐access (ShA, 2‐ h) and long‐access (LgA, 6‐ h) groups and trained to self‐administer methylone or mephedrone (0.5 mg/kg/infusion) using a fixed‐ratio 1 response contingency. The methylone‐trained groups were evaluated on a progressive‐ratio (PR) procedure incorporating dose‐substitution of methylone (0.125–2.5 mg/kg/infusion), mephedrone (0.125–2.5 mg/kg/infusion) or methamphetamine (MA; 0.01–0.5 mg/kg/infusion). Mephedrone‐trained rats were similarly evaluated on a PR with mephedrone and MA. Rats trained with LgA to methylone and mephedrone earned more infusions during acquisition compared with ShA groups. Mephedrone‐trained LgA rats reached significantly higher breakpoints than all other groups in mephedrone and MA PR tests. Methylone‐trained LgA rats exhibited a rightward shift of the peak effective dose but no overall efficacy change compared with methylone‐trained ShA rats. These findings show that the self‐administration of mephedrone escalates under LgA conditions in a manner similar to traditional stimulants whereas escalation of 6 h intakes of methylone is not accompanied by differences in PR performance. Thus mephedrone represents the greater risk for dysregulated drug consumption.

Clinical and Preclinical Evidence for Functional Interactions of Cannabidiol and Δ 9 -Tetrahydrocannabinol

The plant Cannabis sativa, commonly called cannabis or marijuana, has been used for its psychotropic and mind-altering side effects for millennia. There has been growing attention in recent years on its potential therapeutic efficacy as municipalities and legislative bodies in the United States, Canada, and other countries grapple with enacting policy to facilitate the use of cannabis or its constituents for medical purposes. There are >550 chemical compounds and >100 phytocannabinoids isolated from cannabis, including Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD). THC is thought to produce the main psychoactive effects of cannabis, while CBD does not appear to have similar effects. Studies conflict as to whether CBD attenuates or exacerbates the behavioral and cognitive effects of THC. This includes effects of CBD on THC-induced anxiety, psychosis, and cognitive deficits. In this article, we review the available evidence on the pharmacology and behavioral interactions of THC and CBD from preclinical and human studies, particularly with reference to anxiety and psychosis-like symptoms. Both THC and CBD, as well as other cannabinoid molecules, are currently being evaluated for medicinal purposes, separately and in combination. Future cannabis-related policy decisions should include consideration of scientific findings, including the individual and interactive effects of CBD and THC.

Active vaccination attenuates the psychostimulant effects of α-PVP and MDPV in rats

&NA; Recreational use of substituted cathinones continues to be an emerging public health problem in the United States; cathinone derivatives &agr;‐pyrrolidinopentiophenone (&agr;‐PVP) and 3,4‐methylenedioxypyrovalerone (MDPV), which have been linked to human fatalities and show high potential for abuse liability in animal models, are of particular concern. The objective of this study was to develop an immunotherapeutic strategy for attenuating the effects of &agr;‐PVP and MDPV in rats, using drug‐conjugate vaccines created to generate antibodies with neutralizing capacity. Immunoconjugates (&agr;‐PVP‐KLH and MDPV‐KLH) or the control carrier protein, keyhole limpet hemocyanin (KLH), were administered to groups (N = 12) of male Sprague‐Dawley rats on Weeks 0, 2 and 4. Groups were administered &agr;‐PVP or MDPV (0.0, 0.25, 0.5, 1.0, 5.0 mg/kg, i.p.) in acute drug challenges and tested for changes in wheel activity. Increased wheel activity produced by &agr;‐PVP or MDPV in the controls was attenuated in the &agr;‐PVP‐KLH and MDPV‐KLH vaccinated groups, respectively. Rectal temperature decreases produced by MDPV in the controls were reduced in duration in the MDPV‐KLH vaccine group. A separate group (N = 19) was trained to intravenously self‐administer &agr;‐PVP (0.05, 0.1 mg/kg/inf) and vaccinated with KLH or &agr;‐PVP‐KLH, post‐acquisition. Self‐administration in &agr;‐PVP‐KLH rats was initially higher than in the KLH rats but then significantly decreased following a final vaccine booster, unlike the stable intake of KLH rats. The data demonstrate that active vaccination provides functional protection against the effects of &agr;‐PVP and MDPV, in vivo, and recommend additional development of vaccines as potential therapeutics for mitigating the effects of designer cathinone derivatives. HighlightsThe novel drugs alpha‐pyrrolidinopentiophenone (&agr;‐PVP) and 3,4‐methylenedioxypyrovalerone (MDPV) have high abuse potential.There are no currently available therapies to treat stimulant abuse, including MDPV and &agr;‐PVP.Drug‐conjugate vaccines were created to generate antibodies to neutralize MDPV and &agr;‐PVP.Increased wheel activity was produced by &agr;‐PVP or MDPV in the controls but not the vaccinated groups.Self‐administration of &agr;‐PVP was disrupted in the vaccinated group.

Effective active vaccination against methamphetamine in female rats

BACKGROUND Immunotherapies directed against methamphetamine (MA) abuse have shown success in rodent models, however only a limited number of studies have investigated active vaccination in female mice and none in female rats. It is critical to determine if potential immunotherapeutic strategies generalize across sex, particularly for drugs that may produce significant sex-differences on behavioral or physiological endpoints. METHODS Female Wistar rats were initially vaccinated with keyhole-limpet hemocyanin (KLH) or an anti-methamphetamine-KLH conjugate (MH6-KLH) three times over five weeks and implanted with radiotelemetry devices to assess locomotor activity and body temperature responses to MA. Rats were first exposed to MA via vapor inhalation (100mg/mL in propylene glycol) and then by injection (0.25-1.0mg/kg, i.p.) and vapor after a final vaccine boost. RESULTS The MH6-KLH vaccine generated an increase in antibody titers across the initial 6-week, 3 immunization protocol and a restoration of titer after a week 14 booster. Locomotor stimulation induced by 0.25mg/kg MA, i.p, in the KLH group was prevented in the MH6-KLH group. MH6-KLH animals also exhibited an attenuated locomotor stimulation produced by 0.5mg/kg MA, i.p. No group differences in locomotion induced by vapor inhalation of MA were observed and body temperature was not differentially affected by MA across the groups, most likely because vapor inhalation of MA that produced similar locomotor stimulation resulted in ∼10-fold higher plasma MA levels. CONCLUSIONS This study confirms the efficacy of the MH6-KLH vaccine in attenuating the effects of MA in female rats.

Repeated vapor inhalation of Δ9-tetrahydrocannabinol induces tolerance to hypothermia in female rats

Background and Purpose: Tolerance to the effects of Δ9-tetrahydrocannabinol (THC) emerges with repeated exposure, although it varies with dose, chronicity and the measure of interest. THC inhalation via an e-cigarette based system induces hypothermic and antinociceptive effects in rats. This study was conducted to determine if tolerance to these effects could be produced with repeated vapor inhalation. Experimental Approaches: Wistar rats were exposed to 30 minutes of vapor inhalation of the propylene glycol (PG) vehicle and then THC (200 mg/mL in PG) twice per day for four days. Female and male groups were compared for rectal temperature changes and tail-withdrawal latency from a noxious stimulus. A second female group was prepared with radiotelemetry devices for temperature and activity and then exposed to 30 minutes of PG (b.i.d., 4 days) and then THC (100 mg/mL; b.i.d., 5 days). Additional studies evaluated the effects of 4 mg/kg SR141716, AM251 or AM630 i.p. to determine CB1 and CB2 receptor contributions. Key Results: Female, but not male rats developed tolerance to the hypothermic and antinociceptive effects of THC after four days of THC vapor inhalation. The antagonist SR141716 blocked or attenuated antinociceptive effects of acute THC inhalation in male and female rats. Initial hypothermia was not prevented by SR141716 or AM251 but the restoration of normal temperature was accelerated. Conclusions and Implications: Twice daily THC inhalation induces tolerance in female rats, providing further validation of the method. Blockade of the CB1 receptor shortens the maintenance of hypothermia and blocks antinociception after THC inhalation.Rationale A reduced effect of a given dose of Δ9-tetrahydrocannabinol (THC) emerges with repeated exposure to the drug. This tolerance can vary depending on THC dose, exposure chronicity and the behavioral or physiological measure of interest. A novel THC inhalation system based on e-cigarette technology has been recently shown to produce the hypothermic and antinociceptive effects of THC in rats. Objective To determine if tolerance to these effects can be produced with repeated vapor inhalation. Methods Groups of male and female Wistar rats were exposed to 30 minutes of inhalation of the propylene glycol (PG) vehicle or THC (200 mg/mL in PG) two or three times per day for four days. Rectal temperature changes and nociception were assessed after the first exposure on the first and fourth days of repeated inhalation. Results Female, but not male, rats developed tolerance to the hypothermic and antinociceptive effects of THC after four days of twice-daily THC vapor inhalation. Thrice daily inhalation for four days resulted in tolerance in both male and female rats. The plasma THC levels reached after a 30 minute inhalation session did not differ between the male and female rats. Conclusions Repeated daily THC inhalation induces tolerance in female and male rats, providing further validation of the vapor inhalation method for preclinical studies. Abbreviations PG, propylene glycol; THC; Δ9tetrahydrocannabinol;

Repeated Δ9-tetrahydrocannabinol (THC) vapor inhalation during adolescence: Sex differences inacute thermoregulatory tolerance and in feeding during adulthood

Adolescents are regularly exposed to Δ9-tetrahydrocannabinol (THC) via smoking, and, more recently, vaping, cannabis / extracts. Growing legalization of cannabis for medical and recreational purposes, combined with decreasing perceptions of harm, makes it increasingly important to determine the consequences of frequent adolescent exposure for motivated behavior and lasting tolerance in response to THC. Male and female rats inhaled THC vapor, or that from the propylene glycol (PG) vehicle, twice daily for 30 minutes from postnatal day (PND) 35-39 and PND 42-45 using an e-cigarette system. Thermoregulatory responses to vapor inhalation were assessed by radio-telemetry during adolescence and from PND 86-94; chow intake was assessed in adulthood. Blood samples were obtained from additional adolescent groups following initial THC inhalation and after four days of twice daily exposure. Additional groups exposed repeatedly to THC or PG during adolescence were evaluated for intravenous self-administration of oxycodone as adults. Female, not male, adolescents developed tolerance to the hypothermic effects of THC inhalation in the first week of repeated exposure despite similar plasma THC levels. Each sex exhibited tolerance to THC hypothermia in adulthood after repeated adolescent THC with THC greater potency exhibited in females. Repeated-THC male rats consumed more food than their PG treated control group, in the absence of a significant bodyweight difference. Adolescent THC did not alter oxycodone self-administration in either sex, but increased fentanyl self-administration in females. Repeated THC vapor inhalation in adolescent rats results in lasting consequences observable in adulthood.Many US adolescents are regularly exposed to Δ9-tetrahydrocannabinol (THC) via the smoking and more recently, vaping, of cannabis and cannabis extracts. Growing legalization of cannabis for medical and recreational purposes, and decreasing perceptions of harm, make it increasingly important to determine the consequences of frequent adolescent exposure. Male and female Wistar rats were implanted with radio-telemetry devices to monitor body temperature and exposed to twice daily 30 minute inhalation of THC vapor, or the propylene glycol (PG) vehicle, from post-natal day (PND) 35-39 and PND 42-45 using an e-cigarette based system. Responses to THC were re-determined from PND 86-94 and chow intake was assessed in mid adulthood. Blood samples were obtained from additional groups following THC inhalation on PND 31, on PND 39 after a week of twice daily exposure, and during early adulthood. Additional groups of male rats exposed repeatedly to THC or PG during adolescence were evaluated for intravenous self-administration of oxycodone as adults. Female, but not male, adolescents developed tolerance to the hypothermic effects of THC inhalation in the first week of repeated exposure despite similar plasma THC levels. Each sex exhibited tolerance to THC hypothermia in adulthood after repeated adolescent THC with THC exhibiting greater potency in females. Repeated-THC male rats consumed more food than their PG treated control group, in the absence of a significant bodyweight difference, but male rats did not differ in oxycodone self-administration. This study confirms that repeated THC vapor inhalation in adolescence results in lasting consequences observable in adulthood.

Tolerance to hypothermic and antinoceptive effects of ∆9-tetrahydrocannabinol (THC) vapor inhalation in rats.

Rationale: A reduced effect of a given dose of &dgr;9‐tetrahydrocannabinol (THC) emerges with repeated exposure to the drug. This tolerance can vary depending on THC dose, exposure chronicity and the behavioral or physiological measure of interest. A novel THC inhalation system based on e‐cigarette technology has been recently shown to produce the hypothermic and antinociceptive effects of THC in rats. Objective: To determine if tolerance to these effects can be produced with repeated vapor inhalation. Methods: Groups of male and female Wistar rats were exposed to 30 min of inhalation of the propylene glycol (PG) vehicle or THC (200 mg/mL in PG) two or three times per day for four days. Rectal temperature changes and nociception were assessed after the first exposure on the first and fourth days of repeated inhalation. Results: Female, but not male, rats developed tolerance to the hypothermic and antinociceptive effects of THC after four days of twice‐daily THC vapor inhalation. Thrice daily inhalation for four days resulted in tolerance in both male and female rats. The plasma THC levels reached after a 30 min inhalation session did not differ between the male and female rats. Conclusions: Repeated daily THC inhalation induces tolerance in female and male rats, providing further validation of the vapor inhalation method for preclinical studies. HighlightsAn e‐cigarette based THC inhalation system produces hypothermia and antinociception in rats.Tolerance to THC emerges with repeated exposure.Repeated daily THC inhalation induces tolerance in female and male rats.This further validates vapor inhalation of THC in rats as a model of human consumption.

Prophylactic vaccination protects against the development of oxycodone self-administration

ABSTRACT Abuse of prescription opioids is a growing public health crisis in the United States, with drug overdose deaths increasing dramatically over the past 15 years. Few preclinical studies exist on the reinforcing effects of oxycodone or on the development of therapies for oxycodone abuse. This study was conducted to determine if immunopharmacotherapy directed against oxycodone would be capable of altering oxycodone‐induced antinociception and intravenous self‐administration. Male Wistar rats were administered a small‐molecule immunoconjugate vaccine (Oxy‐TT) or the control carrier protein, tetanus toxoid (TT), and trained to intravenously self‐administer oxycodone (0.06 or 0.15mg/kg/infusion). Brain oxycodone concentrations were 50% lower in Oxy‐TT rats compared to TT rats 30min after injection (1mg/kg, s.c.) whereas plasma oxycodone was 15‐fold higher from drug sequestration by circulating antibodies. Oxy‐TT rats were also less sensitive to 1–2mg/kg, s.c. oxycodone on a hot water nociception assay. Half of the Oxy‐TT rats failed to acquire intravenous self‐administration under the 0.06mg/kg/infusion training dose. Oxycodone self‐administration of Oxy‐TT rats trained on 0.15mg/kg/infusion was higher than controls; however under progressive ratio (PR) conditions the Oxy‐TT rats decreased their oxycodone intake, unlike TT controls. These data demonstrate that active vaccination provides protection against the reinforcing effects of oxycodone. Anti‐oxycodone vaccines may entirely prevent repeated use in some individuals who otherwise would become addicted. Vaccination may also reduce dependence in those who become addicted and therefore facilitate the effects of other therapeutic interventions which either increase the difficulty of drug use or incentivize other behaviors. HIGHLIGHTSNon‐medical use of prescription opioids such as oxycodone has reached epidemic levels.This study shows protective effects of an anti‐oxycodone vaccine in rats.Under lower dose conditions half of the rats did not acquire oxycodone self‐administration.Introducing a higher workload decreased intake under higher dose conditions.Anti‐oxycodone vaccination may reduce the incidence and severity of dependence.

Δ9-tetrahydrocannabinol Attenuates Oxycodone Self-Administration Under Extended Access Conditions

Growing nonmedical use of prescription opioids is a significant global problem which motivates research on ways to reduce therapeutic use and combat addiction. Medical marijuana availability has been associated epidemiologically with reduced opioid harms and cannabinoids have been shown to modulate effects of heroin or morphine in animal models. This study was conducted to determine if Δ9-tetrahydrocannabinol (THC) enhances the rewarding and/or antinociceptive effects of oxycodone. Male Wistar rats were trained to intravenously self-administer (IVSA) oxycodone (0.15 mg/kg/infusion) during 1 h or 8 h sessions. After acquisition of oxycodone IVSA, rats were exposed to THC by vapor inhalation (0, 100 or 200 mg/mL in the vehicle; 1 h and 8 h groups) or injection (0, 5 or 10 mg/kg, i.p., 8 h group) prior to IVSA sessions. Oxycodone intake was significantly decreased in rats following vaporized or injected THC compared with vehicle treatment prior to the session. Additional groups of male and female Wistar rats were assessed for nociception of a 52 °C hot water bath following inhalation of vaporized THC (50 mg/mL), oxycodone (100 mg/mL), the THC/oxycodone combination or the PG vehicle. Tail withdrawal latency was increased more by the THC/oxycodone combination compared to either drug alone. Similar additive effects on tail withdrawal latency were produced by injection of THC (5.0 mg/kg, i.p.) and oxycodone (2.0 mg/kg, s.c.). These data show additive effects of THC and oxycodone in rats and suggest the potential use of cannabinoids to enhance therapeutic efficacy and to reduce non-medical opioid abuse.