Knowledge Base: Addiction
Recent studies have shown that the endocannabinoid system is involved in the common neurobiological mechanism underlying drug addiction. This system participates in the primary rewarding effects of cannabinoids, nicotine, alcohol and opioids, through the release of endocannabinoids in the ventral tegmental area. Endocannabinoids are also involved in the motivation to seek drugs by a dopamine-independent mechanism, demonstrated for psychostimulants and opioids. The endocannabinoid system also participates in the common mechanisms underlying relapse to drug-seeking behaviour by mediating the motivational effects of drug-related environmental stimuli and drug reexposure. In agreement, clinical trials have suggested that the CB1 cannabinoid antagonist rimonabant can cause smoking cessation. Thus, CB1 cannabinoid antagonists could represent a new generation of compounds to treat drug addiction.
Substitution can be operationalized as the conscious choice to use one drug (legal or illicit) instead of, or in conjunction with, another due to issues such as: perceived safety; level of addiction potential; effectiveness in relieving symptoms; access and level of acceptance. This practice of substitution has been observed among individuals using cannabis for medical purposes. This study examined drug and alcohol use, and the occurrence of substitution among medical cannabis patients.
Drug addiction is a chronically relapsing disorder characterized by the compulsive desire to use drugs and a loss of control over consumption. Cannabidiol (CBD), the second most abundant component of cannabis, is thought to modulate various neuronal circuits involved in drug addiction. The goal of this systematic review is to summarize the available preclinical and clinical data on the impact of CBD on addictive behaviors. MEDLINE and PubMed were searched for English and French language articles published before 2015. In all, 14 studies were found, 9 of which were conducted on animals and the remaining 5 on humans. A limited number of preclinical studies suggest that CBD may have therapeutic properties on opioid, cocaine, and psychostimulant addiction, and some preliminary data suggest that it may be beneficial in cannabis and tobacco addiction in humans. Further studies are clearly necessary to fully evaluate the potential of CBD as an intervention for addictive disorders.
Cannabidiol, a Nonpsychotropic Component of Cannabis, Inhibits Cue-Induced Heroin Seeking and Normalizes Discrete Mesolimbic Neuronal Disturbances
There remains debate regarding the impact of cannabis on neuropsychiatric disorders. Here, we examined the effects of cannabidiol (CBD), a nonpsychoactive constituent of cannabis, on heroin self-administration and drug-seeking behavior using an experimental rat model. CBD (5–20 mg/kg) did not alter stable intake of heroin self-administration, extinction behavior, or drug seeking induced by a heroin prime injection. Instead, it specifically attenuated heroin-seeking behavior reinstated by exposure to a conditioned stimulus cue. CBD had a protracted effect with significance evident after 24 h and even 2 weeks after administration. The behavioral effects were paralleled by neurobiological alterations in the glutamatergic and endocannabinoid systems. Discrete disturbances of AMPA GluR1 and cannabinoid type-1 receptor expression observed in the nucleus accumbens associated with stimulus cue-induced heroin seeking were normalized by CBD treatment. The findings highlight the unique contributions of distinct cannabis constituents to addiction vulnera- bility and suggest that CBD may be a potential treatment for heroin craving and relapse.
Adolescent Exposure to Chronic Delta-9-Tetrahydrocannabinol Blocks Opiate Dependence in Maternally Deprived Rats
Maternal deprivation in rats specifically leads to a vulnerability to opiate dependence. However, the impact of cannabis exposure during adolescence on this opiate vulnerability has not been investigated. Chronic dronabinol (natural delta-9 tetrahydrocannabinol, THC) exposure during postnatal days 35-49 was made in maternal deprived (D) or non-deprived (animal facility rearing, AFR) rats. The effects of dronabinol exposure were studied after 2 weeks of washout on the rewarding effects of morphine measured in the place preference and oral self-administration tests. The preproenkephalin (PPE) mRNA levels and the relative density and functionality of CB1, and mu-opioid receptors were quantified in the striatum and the mesencephalon. Chronic dronabinol exposure in AFR rats induced an increase in sensitivity to morphine conditioning in the place preference paradigm together with a decrease of PPE mRNA levels in the nucleus accumbens and the caudate-putamen nucleus, without any modification for preference to oral morphine consumption. In contrast, dronabinol treatment on D-rats normalized PPE decrease in the striatum, morphine consumption, and suppressed sensitivity to morphine conditioning. CB1 and mu-opioid receptor density and functionality were not changed in the striatum and mesencephalon of all groups of rats. These results indicate THC potency to act as a homeostatic modifier that would worsen the reward effects of morphine on naive animals, but ameliorate the deficits in maternally D-rats. These findings point to the self-medication use of cannabis in subgroups of individuals subjected to adverse postnatal environment.