Cannabidiol may prevent sensitization to cocaine and caffeine by influencing brain structure genes

A new study published in the journal Addiction Neuroscience provides evidence that cannabidiol may help prevent the heightened behavioral response associated with the combined use of cocaine and caffeine. The research suggests that this protective effect occurs because cannabidiol influences the activity of specific genes related to the structure and organization of brain cells in the reward system. These findings offer a potential biological explanation for how this cannabis-derived compound might assist in the treatment of stimulant use disorders.

Cocaine dependence represents a significant public health challenge with few effective pharmaceutical treatments available. In the illicit drug market, cocaine is frequently mixed with other active substances to increase profits or alter the drug’s effects. Forensic data indicates that caffeine is one of the most common adulterants found in seized cocaine samples.

Previous observations suggest that adding caffeine to cocaine does more than just dilute the product. This combination appears to accelerate the development of addiction-like behaviors and enhances the stimulating effects of cocaine. The mixture can lead to more intense drug-seeking behavior and persistent changes in the brain compared to cocaine alone.

The scientific team sought to understand the underlying molecular mechanisms that allow cannabidiol to counteract these enhanced effects. They specifically looked at how cannabidiol affects gene expression in the brain when an animal is exposed to this drug mixture. José Pedro Prieto from the Department of Experimental Neuropharmacology at the Instituto de Investigaciones Biológicas Clemente Estable in Uruguay served as the first author of the paper.

The researchers conducted their experiments using 26 male C57BL/6 mice. They employed a behavioral protocol known as locomotor sensitization to measure the animals’ reactions to the drugs. This method tracks how much the animals move in an open field environment after receiving specific substances.

An increase in movement over time in response to the same dose of a drug typically indicates a sensitized, addiction-like response. The study was designed to see if pretreatment with cannabidiol could stop this escalation in movement. The experimental schedule spanned several days to assess both the immediate effects and the lasting changes.

The mice first underwent a habituation period to become accustomed to the testing environment. For three consecutive days, the animals received an injection of either cannabidiol or a control vehicle. Thirty minutes after this first injection, they received a combined injection of cocaine and caffeine or a saline solution.

Following this three-day pretreatment phase, the mice experienced a five-day period without any drugs. This drug-free interval allows the brain to process the previous exposure and mimics periods of abstinence. On the final day of the experiment, known as the challenge day, all mice received the cocaine and caffeine mixture to test their reaction.

The researchers recorded the total distance the mice moved during the open field tests. The group that received the cocaine and caffeine mixture without prior cannabidiol treatment showed a significant increase in movement over the three days. On the challenge day, these mice displayed high levels of locomotor activity, confirming they had developed sensitization.

In contrast, the mice pretreated with cannabidiol displayed significantly lower locomotor activity on the challenge day. Their movement levels were comparable to mice that had not been sensitized to the stimulants. This indicates that the cannabidiol treatment effectively prevented the expression of locomotor sensitization.

Immediately after the behavioral tests on the challenge day, the scientists collected tissue from the nucleus accumbens of the mice. The nucleus accumbens is a brain region that plays a central role in processing reward, motivation, and reinforcement. The team extracted genetic material from this tissue to perform high-throughput RNA sequencing.

This advanced genetic technique allowed the researchers to identify which genes were active or inactive in the different groups of mice. They looked for patterns of gene expression that correlated with the behavioral results. The analysis revealed that cannabidiol treatment led to distinct and broad changes in genetic activity.

The study highlighted a significant enrichment of genes involved in the organization of the extracellular matrix in the cannabidiol-treated groups. The extracellular matrix is a complex network of proteins and other molecules that provides structural and biochemical support to surrounding cells. It plays a vital role in synaptic plasticity, which is the brain’s ability to reorganize itself.

Key genes such as Tnc (Tenascin C), Acta2, and Col5a2 showed increased activity in the groups that received cannabidiol. These genes are directly involved in maintaining and remodeling the structure of the extracellular matrix. The data suggests that cannabidiol may reinforce this structural network in a way that prevents the maladaptive changes caused by stimulants.

The researchers also identified a specific gene called Entpd4b that showed a distinct pattern of expression. This gene was highly active in the sensitized mice that did not receive cannabidiol. However, in the group treated with cannabidiol, the activity of Entpd4b was significantly reduced.

This specific gene encodes an enzyme involved in nucleotide recycling, which may be linked to adenosine production. The researchers propose that the high levels of this gene in sensitized animals might be a compensatory mechanism for the blockage of adenosine receptors by caffeine. Cannabidiol appears to normalize this response.

Beyond structural genes, the analysis pointed to the involvement of anti-inflammatory pathways. Neuroinflammation is increasingly recognized as a contributing factor to the neural adaptations seen in addiction. The study found that genes related to inflammation regulation were influenced by cannabidiol.

Specifically, the protein Tenascin C, encoded by the Tnc gene, is known to participate in both immune responses and tissue repair. Its upregulation in the protected group suggests a link between the structural remodeling of the brain and the regulation of inflammation. The researchers propose that cannabidiol helps limit the inflammatory signaling that typically accompanies repeated stimulant use.

The study also noted an enrichment of the brain-derived neurotrophic factor signaling pathway in the cannabidiol-treated mice. This protein supports the survival of existing neurons and encourages the growth of new synapses. Interactions between this pathway and the extracellular matrix are necessary for neural plasticity.

By modulating these pathways, cannabidiol may prevent the brain from “learning” the addictive behavior associated with the cocaine and caffeine mixture. The stabilization of the extracellular matrix could physically or chemically restrict the synaptic changes that drive sensitization. This provides a novel perspective on how cannabidiol exerts its effects.

One potential limitation of the study involves the composition of the sample. The experiment used only male mice, which means the results might not fully translate to females. Biological sex can influence how the brain responds to drugs and how it metabolizes treatments. Future studies will need to include female subjects to determine if the protective effects are consistent across sexes.

Another limitation is the relatively small sample size used for the genetic sequencing. While the size was sufficient for this type of exploratory analysis, a larger number of subjects could help detect more subtle changes in gene expression. The complexity of the gene networks means that some minor but relevant pathways might have been missed.

It is also important to note that this research was conducted on animal models using a specific dosing schedule. The transition from preclinical animal studies to human application is not always direct. The doses and timing used in mice may not have an exact equivalent in human therapeutic contexts.

Readers should interpret these findings as a step toward understanding the biological targets of cannabidiol. The study identifies the extracellular matrix as a promising area for future drug development. It does not, however, suggest that cannabidiol is a cure for addiction in its current form.

Future research aims to verify these genetic targets by manipulating them directly. Scientists could inhibit or activate the specific extracellular matrix genes identified to see if that replicates or blocks the effects of cannabidiol. Additionally, further work is needed to see if these mechanisms apply to other types of addictive substances.

The study, “Canabidiol prevents cocaine and caffeine sensitization modulating expression of extracellular matrix genes in the Nucleus Accumbens of male mice,” was authored by José Pedro Prieto, Rafael Sebastián Fort, Guillermo Eastman, Evangelina Coitiño, Oliver Kaminski, Carlos Ferreiro-Vera, Verónica Sanchez de Medina, María Ana Duhagon, Cecilia Scorza, and José Roberto Sotelo-Silveira.