Cannabidiol regulates behavioural alterations and gene expression changes induced by spontaneous cannabinoid withdrawal
Francisco Navarrete, Auxiliadora Aracil-Fernández and Jorge Manzanares
British Journal of Pharmacology, 2018.
Doi : 10.1111/bph.14226
BACKGROUND AND PURPOSE
Cannabidiol (CBD) represents a promising therapeutic tool for treating cannabis use disorder (CUD). This study aimed to evaluate the effects of CBD on the behavioural and gene expression alterations induced by spontaneous cannabinoid withdrawal.
Spontaneous cannabinoid withdrawal was evaluated 12 h after cessation of CP-55,940 treatment (0.5 mg·kg1 every 12 h, i.p.; 7 days) in C57BL/6J mice. The effects of CBD (5, 10 and 20 mg·kg1, i.p.) on withdrawal-related behavioural signs were evaluated by measuringmotor activity, somatic signs and anxiety-like behaviour. Furthermore, gene expression changes in TH in the ventral tegmental area, and in the opioid μ receptor (Oprm1), cannabinoid CB1 receptor (Cnr1) and CB2 receptor (Cnr2) in the nucleus accumbens, were also evaluated using the real-time PCR technique.
The administration of CBD significantly blocked the increase inmotor activity and the increased number of rearings, rubbings and jumpings associated with cannabinoid withdrawal, and it normalized the decrease in the number of groomings. However, CBD did not change somatic signs in vehicle-treated animals. In addition, the anxiogenic-like effect observed in abstinent mice disappeared with CBD administration, whereas CBD induced an anxiolytic-like effect in non-abstinent animals. Moreover, CBD normalized gene expression changes induced by CP-55,940-mediated spontaneous withdrawal.
CONCLUSIONS AND IMPLICATIONS
The results suggest that CBD alleviates spontaneous cannabinoid withdrawal and normalizes associated gene expression changes. Future studies are needed to determine the relevance of CBD as a potential therapeutic tool for treating CUD.
AEA, anandamide; CBD, cannabidiol; CB receptor, cannabinoid receptor; CUD, cannabis use disorder; FAAH, fatty acid; amide hydrolase; NAcc, nucleus accumbens; SMART, Spontaneous Motor Activity Recording and Tracking; THC, Δ9-tetrahydrocannabinol; VTA, ventral tegmental area
Cannabis preparations, such as hashish and marijuana, are the most commonly used illicit drugs worldwide. The data available suggest that their consumption will continue to rise in coming years, representing a serious public health problem (Volkow et al., 2014). Approximately 24% of patients initiating treatment for substance abuse are diagnosed with cannabis use disorder (CUD) (Danovitch and Gorelick, 2012).
According to the latestWorld Drug Report (United Nations Office on Drugs and Crime, 2016), around 182.5 million people used cannabis in 2016. To date, neither the European Medicine Agency nor the
US Food and Drug Administration have approved any medications for treating CUD; however, different pharmacological approaches have been developed. These fall into two main categories:medications that attenuate symptoms of cannabis withdrawal and/or those that reduce subjective and reinforcing effects of cannabis (for a recent review, see Copeland and Pokorski, 2016). About half the patients treated for CUD report symptoms of a withdrawal syndrome. As these symptoms can serve as a negative reinforcement for relapse to cannabis use in individuals trying to abstain (Levin et al., 2010), cannabis withdrawal should be a focus of treatment. Previous clinical trials have evaluated the therapeutic usefulness of different pharmacological approaches for managing cannabis withdrawal and modulating the reinforcing effects and craving for cannabis, with inconsistent results (Danovitch and Gorelick, 2012). However, the overall clinical outcome in the treatment arms of randomized trials is poor,
and fewer than 20% of participants achieve long-term abstinence (Stephens and Roffman, 2006). In spite of the animal models developed to analyse cannabis abuse liability (Justinova et al., 2005), limited knowledge of the neurochemical mechanisms underlying CUD may contribute, at least in part, to the low efficacy of the medications evaluated to date.
Therefore, it is necessary to invest effort and resources into identifying new drugs that, alone or in combination,may improve the efficacy of CUD treatment. Recent clinical data suggest that cannabidiol (CBD), one of the main constituents of the Cannabis sativa plant, may hold promise as a therapeutic tool for managing CUD.
Our group has recently shown that unlike Δ9-tetrahydrocannabinol (THC), CBD is devoid of rewarding psychotropic properties (Manzanares et al., 2016). Studies in animal models have shown that CBD presents anxiolytic (for a recent review, see Blessing et al., 2015), antidepressant (Zanelati et al., 2010; Schiavon et al., 2016) and antipsychotic properties (Zuardi et al., 1995; Leweke et al., 2012). Although the exact mechanisms underlying these effects remain unclear (Campos et al., 2012b), some authors have posited that CBD modulates the function of more than 65 targets in the CNS (Ibeas Bih et al., 2015), including cannabinoid receptors (CB1 and CB2) and GPR55, the vanilloid receptor TRPV1, the 5-HT1A receptor (Bisogno et al., 2001; Russo et al., 2005; Ryberg et al., 2007; Thomas et al., 2007; Campos et al., 2012a), the anandamide (AEA)-hydrolysing enzyme [fatty acid amide hydrolase (FAAH)] and the adenosine transporter (Carrier et al., 2006; Massi et al., 2008).
However, additional studies are needed to fully determine CBD’s target engagement profile. Previous clinical results point to the therapeutic usefulness of combining CBD with THC as a ‘cannabinoid replacement therapy’ to modulate cannabinoid withdrawal (Allsop et al., 2015). Combination therapy with THC plus CBD in an oromucosal spray (nabiximols or Sativex in the United States of America or European Union, respectively) shows some interesting therapeutic benefits. Indeed, a recent clinical trial demonstrated that nabiximols suppressed cannabis withdrawal symptoms and achieved successful retention in treatment (Allsop et al., 2014). Two additional studies showed that Sativex produces a significant reduction in cannabis withdrawal score, craving and cannabis consumption levels (Trigo et al., 2016a; Trigo et al., 2016b). However, the presence of THC in nabiximols/Sativex preparations could be problematic, especially in (still unexplored) long-term treatment, since it may be associated with THC-related negative psychoactive effects. Thus, recent interest has turned to clinically evaluating CBD alone for managing CUD-related problems. Crippa et al. (2013) found that CBD monotherapy led to a
rapid decrease in cannabis withdrawal symptoms. Another clinical study, comparing p.o. CBD alone versus placebo, found no difference between groups for cannabis-induced subjective effects (Haney et al., 2016). These reports join a raft of ongoing clinical trials evaluating the effects of CBD alone for CUD (Mclean Hospital, NCT03102918), cannabis dependence (University College, London, NCT02044809),
cannabis withdrawal (The University of New South Wales, NCT02083874) or smoked marijuana’s (5.6% THC) subjective, reinforcing, cognitive and cardiovascular effects (National Institute on Drug Abuse, NCT01844687). In the context of this increasing interest in CBD for managing CUD, studies using animal models are crucial to providing information about the therapeutic potential of CBD and the underlying neurobiological mechanisms involved.
The objective of this study is to evaluate the effects of CBD on the spontaneous withdrawal induced by the repeated administration of the potent synthetic cannabinoid receptor agonist CP-55,940 (Devane et al., 1988; Wiley et al., 1995; Oliva et al., 2003; 2004; Aracil-Fernandez et al., 2013) in C57BL/6Jmice. Motor activity (distance travelled in the open field test), withdrawal-related somatic signs (number of rearings, groomings, rubbings and jumpings evaluated in the open field test) and the anxiety-like response (light–dark box test) were assessed 12 h after the last administration of CP-55,940.
Furthermore, gene expression analyses by realtime PCR were carried out to evaluate the changes induced by cannabinoid withdrawal in specific key targets involved in cannabinoid addiction and withdrawal (Romero et al., 1998; Corchero et al., 1999; Manzanares et al., 1999; Oliva et al., 2003, 2004; Lupica et al., 2004; Corchero et al., 2004a, b; Fattore et al., 2008; Aracil-Fernandez et al., 2013), namely, TH in the ventral tegmental area (VTA), and the opioid μ receptor (Oprm1), CB1 receptor (Cnr1) andCB2 receptor (Cnr2) in the nucleus accumbens (NAcc). Briefly, TH is the ratelimiting enzyme for dopamine synthesis in the VTA, playing a pivotal role in the rewarding effects of cannabinoids. Similarly, the μ receptor in the NAcc plays a crucial role in the reinforcing actions of cannabinoid drugs, increasing the release of endogenous opioid peptides that in turn enhance the dopamine tone. Finally, CB1 and CB2 receptors directly modulate the neurobiological actions produced by the administration of cannabinoid compounds.