Cannabidiol Prevents the Expression of the Locomotor Sensitization and the Metabolic Changes in the Nucleus Accumbens and Prefrontal Cortex Elicited by the Combined Administration of Cocaine and Caffeine in Rats.

In the last years, clinical and preclinical researchers have increased their interest in non-psychotomimetic cannabinoids, like cannabidiol (CBD), as a strategy for treating psychostimulant use disorders. However, there are discrepancies in the pharmacological effects and brain targets of CBD. We evaluated if CBD was able to prevent the locomotor sensitization elicited by cocaine and caffeine co-administration. The effect of CBD on putative alterations in the metabolic activity of the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc), and its respective subregions (cingulated, prelimbic, and infralimbic cortices, and NAc core and shell) associated to the behavioral response, was also investigated. Rats were intraperitoneally and repeatedly treated with CBD (20 mg/kg) or its vehicle, followed by the combination of cocaine and caffeine (Coc+Caf; 5 mg/kg and 2.5 mg/kg, respectively) or saline for 3 days. After 5 days of withdrawal, all animals were challenged with Coc+Caf (day 9). Locomotor activity was automatically recorded and analyzed by a video-tracking software. The metabolic activity was determined by measuring cytochrome oxidase-I (CO-I) staining. Locomotion was significantly and similarly increased both in Veh-Coc+Caf- and CBD-Coc+Caf-treated animals during the pretreatment period (3 days); however, on day 9, the expression of the sensitization was blunted in CBD-treated animals. A hypoactive metabolic response and a hyperactive metabolic response in mPFC and NAc subregions respectively were observed after the behavioral sensitization. CBD prevented almost all these changes. Our findings substantially contribute to the understanding of the functional changes associated with cocaine- and caffeine-induced sensitization and the effect of CBD on this process.

A Single Administration of the Atypical Psychedelic Ibogaine or Its Metabolite Noribogaine Induces an Antidepressant-Like Effect in Rats.

Anecdotal reports and open-label case studies in humans indicated that the psychedelic alkaloid ibogaine exerts profound antiaddictive effects. Ample preclinical evidence demonstrated the efficacy of ibogaine, and its main metabolite, noribogaine, in substance-use-disorder rodent models. In contrast to addiction research, depression-relevant effects of ibogaine or noribogaine in rodents have not been previously examined. We have recently reported that the acute ibogaine administration induced a long-term increase of brain-derived neurotrophic factor mRNA levels in the rat prefrontal cortex, which led us to hypothesize that ibogaine may elicit antidepressant-like effects in rats. Accordingly, we characterized behavioral effects (dose- and time-dependence) induced by the acute ibogaine and noribogaine administration in rats using the forced swim test (FST, 20 and 40 mg/kg i.p., single injection for each dose). We also examined the correlation between plasma and brain concentrations of ibogaine and noribogaine and the elicited behavioral response. We found that ibogaine and noribogaine induced a dose- and time-dependent antidepressant-like effect without significant changes of animal locomotor activity. Noribogaine's FST effect was short-lived (30 min) and correlated with high brain concentrations (estimated >8 µM of free drug), while the ibogaine's antidepressant-like effect was significant at 3 h. At this time point, both ibogaine and noribogaine were present in rat brain at concentrations that cannot produce the same behavioral outcome on their own (ibogaine ∼0.5 µM, noribogaine ∼2.5 µM). Our data suggests a polypharmacological mechanism underpinning the antidepressant-like effects of ibogaine and noribogaine.

Molecular changes in the nucleus accumbens and prefrontal cortex associated with the locomotor sensitization induced by coca paste seized samples.

RATIONALE: In previous studies, we have demonstrated that seized samples of a smokable form of cocaine, also known as coca paste (CP), induced behavioral sensitization in rats. Interestingly, this effect was accelerated and enhanced when the samples were adulterated with caffeine. While the cocaine phenomenon is associated with persistent functional and structural alterations in the prefrontal cortex (PFC) and nucleus accumbens (NAc), the molecular mechanisms underlying the CP sensitization and the influence of caffeine remains still unknown. OBJECTIVE: We examined the gene expression in NAc and mPFC after the expression caffeine-adulterated and non-adulterated CP locomotor sensitization. METHODS: The locomotor sensitization was established in C57BL/6 mice, repeatedly treated with a CP-seized sample adulterated with caffeine (CP-2) and a non-adulterated one (CP-1). We then assessed the mRNA expression of receptor subunits of the dopaminergic and glutamatergic systems in the medial PFC (mPFC) and NAc. Other molecular markers (e.g., adenosinergic, endocannabinoid receptor subunits, and synaptic plasticity-associated genes) were also analyzed. RESULTS: Only CP-2-treated mice expressed locomotor sensitization. This phenomenon was associated with increased Drd1a, Gria1, Cnr1, and Syn mRNA expression levels in the NAc. Drd3 mRNA expression levels were only significantly increased in mPFC of CP-2-treated group. CONCLUSIONS: Our results demonstrated that caffeine actively collaborates in the induction of the molecular changes underlying CP sensitization. The present study provides new knowledge on the impact of active adulterants to understand the early dependence induced by CP consumption.

Ibogaine Administration Modifies GDNF and BDNF Expression in Brain Regions Involved in Mesocorticolimbic and Nigral Dopaminergic Circuits.

Ibogaine is an atypical psychedelic alkaloid, which has been subject of research due to its reported ability to attenuate drug-seeking behavior. Recent work has suggested that ibogaine effects on alcohol self-administration in rats are related to the release of Glial cell Derived Neurotrophic Factor (GDNF) in the Ventral Tegmental Area (VTA), a mesencephalic region which hosts the soma of dopaminergic neurons. Although previous reports have shown ibogaine's ability to induce GDNF expression in rat midbrain, there are no studies addressing its effect on the expression of GDNF and other neurotrophic factors (NFs) such as Brain Derived Neurotrophic Factor (BDNF) or Nerve Growth Factor (NGF) in distinct brain regions containing dopaminergic neurons. In this work, we examined the effect of ibogaine acute administration on the expression of these NFs in the VTA, Prefrontal Cortex (PFC), Nucleus Accumbens (NAcc) and the Substantia Nigra (SN). Rats were i.p. treated with ibogaine 20 mg/kg (I20), 40 mg/kg (I40) or vehicle, and NFs expression was analyzed after 3 and 24 h. At 24 h an increase of the expression of the NFs transcripts was observed in a site and dose dependent manner. Only for I40, GDNF was selectively upregulated in the VTA and SN. Both doses elicited a large increase in the expression of BDNF transcripts in the NAcc, SN and PFC, while in the VTA a significant effect was found only for I40. Finally, NGF mRNA was upregulated in all regions after I40, while I20 showed a selective upregulation in PFC and VTA. Regarding protein levels, an increase of GDNF was observed in the VTA only for I40 but no significant increase for BDNF was found in all the studied areas. Interestingly, an increase of proBDNF was detected in the NAcc for both doses. These results show for the first time a selective increase of GDNF specifically in the VTA for I40 but not for I20 after 24 h of administration, which agrees with the effective dose found in previous self-administration studies in rodents. Further research is needed to understand the contribution of these changes to ibogaine's ability to attenuate drug-seeking behavior.

Identification and Quantification of Cocaine and Active Adulterants in Coca-Paste Seized Samples: Useful Scientific Support to Health Care.

Adulteration is a common practice in the illicit drugs market, but the psychoactive and toxic effects provided by adulterants are clinically underestimated. Coca-paste (CP) is a smokable form of cocaine which has an extremely high abuse liability. CP seized samples are sold adulterated; however, qualitative and quantitative data of CP adulteration in forensic literature is still scarce. Besides, it is unknown if adulterants remain stable when CP is heated. This study was designed to report the chemical content of an extensive series of CP seized samples and to demonstrate the stability (i.e., chemical integrity) of the adulterants heated. To achieve this goal, the following strategies were applied: (1) a CP adulterated sample was heated and its fume was chemically analyzed; (2) the vapor of isolated adulterants were analyzed after heating; (3) plasma levels of animals exposed to CP and adulterants were measured. Ninety percent of CP seized samples were adulterated. Adulteration was dominated by phenacetin and caffeine and much less by other compounds (i.e., aminopyrine, levamisole, benzocaine). In the majority of CP analyzed samples, both cocaine and caffeine content was 30%, phenacetin 20% and the combination of these three components reached 90%. Typical cocaine pyrolysis compounds (i.e., BA, CMCHTs, and AEME) were observed in the volatilized cocaine and CP sample but no pyrolysis compounds were found after isolated adulterants heating. Cocaine, phenacetin, and caffeine were detected in plasma. We provide current forensic data about CP seized samples and demonstrated the chemical integrity of their adulterants heated.

Caffeine Induces a Stimulant Effect and Increases Dopamine Release in the Nucleus Accumbens Shell Through the Pulmonary Inhalation Route of Administration in Rats.

Oral, intraperitoneal, or intravenous have been the common routes of administration used to study the behavioral and neurochemical pharmacology of caffeine, one of the most widely used psychoactive substances worldwide. We have reported that caffeine is an active adulterant frequently found in coca-paste (CP)-seized samples, a highly addictive form of smokable cocaine. The role of caffeine in the psychostimulant and neurochemical effects induced by CP remains under study. No preclinical animal studies have been performed so far to characterize the effects of caffeine when it is administered through the pulmonary inhalation route. Caffeine (10, 25, and 50 mg) was volatilized and rats were exposed to one inhalation session of its vapor. The stimulant effect was automatically recorded and plasmatic levels of caffeine were measured. Caffeine capability (50 mg) to increase extracellular dopamine (DA) levels in nucleus accumbens shell was also studied by in vivo microdialysis in non-anesthetized animals. A dose-dependent stimulant effect induced by volatilized caffeine was observed and this effect was directly related with caffeine plasmatic levels. A significant increase in the extracellular DA was achieved after 50 mg of volatilized caffeine exposure. This is the first report showing pharmacological acute effects of caffeine through the pulmonary inhalation route of administration and suggests that this could be a condition under which caffeine can elevate its weak reinforcing effect and even enhance the psychostimulant effect and abuse liability of smokable adulterated psychostimulant drugs.

Caffeine, a common active adulterant of cocaine, enhances the reinforcing effect of cocaine and its motivational value.

RATIONALE: Caffeine is one of the psychoactive substances most widely used as an adulterant in illicit drugs, such as cocaine. Animal studies have demonstrated that caffeine is able to potentiate several cocaine actions, although the enhancement of the cocaine reinforcing property by caffeine is less reported, and the results depend on the paradigms and experimental protocols used. OBJECTIVES: We examined the ability of caffeine to enhance the motivational and rewarding properties of cocaine using an intravenous self-administration paradigm in rats. Additionally, the role of caffeine as a primer cue during extinction was evaluated. METHODS: In naïve rats, we assessed (1) the ability of the cocaine (0.250-0.125 mg/kg/infusion) and caffeine (0.125-0.0625 mg/kg/infusion) combination to maintain self-administration in fixed ratio (FR) and progressive ratio (PR) schedules of reinforcement compared with cocaine or caffeine alone and (2) the effect of caffeine (0.0625 mg/kg/infusion) in the maintenance of responding in the animals exposed to the combination of the drugs during cocaine extinction. RESULTS: Cocaine combined with caffeine and cocaine alone was self-administered on FR and PR schedules of reinforcement. Interestingly, the breaking point determined for the cocaine + caffeine group was significantly higher than the cocaine group. Moreover, caffeine, that by itself did not maintain self-administration behavior in naïve rats, maintained drug-seeking behavior of rats previously exposed to combinations of cocaine + caffeine. CONCLUSIONS: Caffeine enhances the reinforcing effects of cocaine and its motivational value. Our results highlight the role of active adulterants commonly used in cocaine-based illicit street drugs.

Anti-aggressive effect elicited by coca-paste in isolation-induced aggression of male rats: influence of accumbal dopamine and cortical serotonin.

Coca-paste (CP), an illicit drug of abuse, has been frequently associated with aggressive and impulsive behaviors in humans. However, preclinical studies have not been carried out in order to characterize CP effects on aggression. The acute effect of CP, cocaine and caffeine (the main adulterant present in seized samples) on aggression was assessed using the isolation-induced aggression paradigm in male rats. The dopaminergic (DA) neurotransmission in the nucleus accumbens (NAcc) and serotonergic (5-HT) activity in the frontal cortex were explored. CP and cocaine induced a similar anti-aggressive effect on isolated rats although CP-treated animals showed a shorter latency to the first attack. Aggressive behavior was not increased per se by caffeine. Social investigation time was slightly reduced only by cocaine while exploratory activity and time spent walking were increased by the three drugs. Accumbal DA levels were significantly augmented by CP, cocaine and caffeine, although differences in DOPAC and HVA levels were evidenced. A decrease in DA turnover was only observed after CP and cocaine administration. Increased cortical 5-HT levels with a concomitant decrease in 5-HT turnover were observed after CP and cocaine whereas caffeine did not alter it. As cocaine but not caffeine reduced aggression, it seems like cocaine content was mainly responsible for CP anti-aggressive action; however, the presence of caffeine in CP may have a role in the shorter latency to attack compared to cocaine. Despite the increase in NAcc DA, the enhancement of cortical 5-HT levels can likely underlie the anti-aggression observed in CP-treated animals.

Coca-paste seized samples characterization: chemical analysis, stimulating effect in rats and relevance of caffeine as a major adulterant.

Coca-paste (CP) is a drug of abuse that so far has not been extensively characterized. CP is an intermediate product of the cocaine alkaloid extraction process from coca leaves, hence it has a high content of cocaine base mixed with other chemical substances (impurities) and it is probably adulterated when it reaches the consumers. Despite its high prevalence and distribution through South America, little is known about its effects on the central nervous system. In the present study, a chemical analysis of CP samples from different police seizures was performed to determine the cocaine base content and the presence and content of impurities and adulterants. Some CP representative samples were selected to study the effects on the locomotor activity induced after acute systemic administration in rats as a measure of its stimulant action. The behavioral response was compared to equivalent doses of cocaine. As expected, cocaine was the main component in most of the CP samples assayed. Caffeine was the only active adulterant detected. Interestingly, several CP samples elicited a higher stimulant effect compared to that observed after cocaine when administered at equivalent doses of cocaine base. Combined treatment of cocaine and caffeine, as surrogate of different CP samples mimicked their stimulant effect. We demonstrated that cocaine and caffeine are the main components responsible for the CP-induced stimulant action while the contribution of the impurities was imperceptible.