There is an increasing interest in the use of cocaine alongside other drugs of abuse, particularly marijuana.
Some have investigated this within the context of public health by observing the effect that these substances may have in common, yet fatal, conditions such as heart disease.
Existing data suggests a detrimental link between marijuana and cocaine use, and adverse health outcomes in those who co-abuse these substances. However, until recently there has been no research that has explored the potential of cannabis to reinforce the effects of cocaine in people who use both substances.
One of the few studies conducted in this area was undertaken by researchers at the Wake Forest School of Medicine. The findings provided evidence of a correlational link between cannabis and the frequency and dose of cocaine use and provided unique insights about its significance.
The study was recently published in the Journal of Pharmacology and Experimental Therapeutics. It was the first of its kind to assess the ability of cannabis to influence the choice behavior of laboratory monkeys who were given the option to self-administer cocaine in lieu of food.
“Response allocation” refers to daily behaviors that are required for survival, such as eating, drinking, and sleeping. Ideally, these will be evenly distributed throughout the day. The potential for this balance to be disrupted in favor of pursuing desirable behaviors that are not conducive to survival has been a topic of interest for many scientific studies, particularly those focused on drugs of abuse.
Researchers used several agents that act upon cannabinoid receptors within the body in differing degrees of strength. Cannabinoid receptors are present in humans and monkeys and function the same in both. The main psychoactive chemical within marijuana, delta-9-tetrahydrocannabinol (THC), acts as a partial stimulator upon the cannabinoid receptor. Other chemical agents either act to fully or partially stimulate this receptor or to inhibit it.
Laboratory monkeys in this study were pretreated with 3 different agents that acted to partially stimulate, completely stimulate, or inhibit the effects of the cannabinoid receptor. After the administration of each agent, researchers observed whether the monkeys chose to forgo food in favor of substances that contained varying strengths of cocaine, including a substance that did not contain cocaine.
Monkeys pretreated with low doses of THC, the active chemical in cannabis, chose cocaine with greater frequency coinciding with increasing doses of THC. Similarly, monkeys treated with higher doses of THC chose to self-administer greater strengths of cocaine in lieu of food. The greater strength of the pre-administered dose of THC was associated with an increased likelihood that monkeys would choose to neglect food for cocaine.
Interestingly, rimonabant, a blocker of cannabinoid receptors, had a similar effect on cocaine use as THC. The observation that increasing strengths of pre-administered THC and rimonabant doses positively correlated with increases in the frequency and strength of cocaine dose chosen, alongside greater neglect of food-choice, suggests that the pre-administered substances reinforce the effect of cocaine.
Another finding of particular interest was that pre-administration of CP 55,940, an agent that fully stimulates cannabinoid receptors decreased cocaine choice and dose strength. Consistent with these findings, monkeys administered CP 55,940 were noted to increasingly choose food when administered progressively greater strengths of this agent. Researchers noted the ability of CP 55,940 to reduce the reinforcing strength of cocaine, and plan to further evaluate the role of this substance in the context of cocaine choice.
Findings demonstrated that tolerance to the effects of CP 55,940 developed after being pre-treated with this substance for 7 days. After this period CP 55,940 had reduced efficacy in mitigating cocaine choice, with monkeys beginning to choose cocaine with greater frequency despite CP 55,940 administration.
Significance and Limitations
Although there have been prior studies suggesting a possible link between cannabis, its compounds, and the potential for chemical constituents to reinforce the preference for cocaine, this was the first study of its kind to explore this systematically. By utilizing a procedure whereby data on food-cocaine choice could be collected and analyzed, it was able to provide a unique vantage point in the assessment of response allocation and its ability to be manipulated. In doing so, this research adds depth to the current understanding of the effects of cannabis and cocaine.
The findings also have important implications for public health and drug abuse. Although this study used animals in its investigation, the results still hold validity and most importantly provide insights for future research within this realm. This can be used to not only understand but help those who suffer from cocaine addiction, as many who use cocaine also concurrently use cannabis.
Of particular note, the potential utility of CD 55,940, or other agents that influence cannabinoid receptors to reduce preference for cocaine, merit further exploration based on the results of this study.
It is important to take note of the litany of factors that may influence the progression of addiction, including those variables which have yet to be discovered. Through the findings provided by studies like this, we arrive ever closer to achieving massive improvements in our ability to help those who suffer from substance abuse and dependence.