A few weeks ago, my lab mates and I were discussing results from our current cocaine-centric experimental protocols, when my lab mate remarked; “Who does cocaine anymore??? That’ so 80′s and early 90′s!”
Much like these:
Neo-drugs of abuse today include methamphetamines, X, and any other stimulant designed to extend wakefulness and improve cognitive performance in today’s every-increasing high-pressure, information-overload society. Read the awesome blog Drug Monkey for more info on these drugs’ prevalence of use and abuse.
In support of “cocaine….that’s so 80s” hypothesis, a recent paper in PLoS highlighted the weak addictive potential of cocaine relative to other rewards, particularly non-drugs rewards such as sweets. Hypersensitization (i.e. highly active animal and cascades of excitatory neurotransmitter release), a hallmark of cocaine use, often overestimates the currently thought rewarding and addictive properties of this drug, resulting in cocaine to rank higher on ladder rung of addictive drugs.
Using a procedural ratio task (must increasingly work (i.e. lever press) for a reward) and subsequent extinction (i.e. a period in which repeated lever presses will not elicit a reward; see previous post) and choice-preference (equal opportunity to obtain one of two rewards), the project researchers found the following.
First, the rats will more quickly lever press for a cocaine reward (breaking point) and will subsequently administer more cocaine relative to taste of sweetened (uncaloric) water. This is show here.
To assess whether this hyper-responding to cocaine was due to its addictive potential or simply was an artifact of cocaine’s stimulating properties (just can’t help being active), the researchers extended the latency to which a lever press would elicit a reward from immediately to 10-minutes. Turns out, that the rats were more willing to work for the sweetened-solution over cocaine under this circumstance.
And lever-pressing was more prolonged during extinction (an indication of habit-forming behavior) in the sweet-treated group.
This was secondarily supported by evidence that in a free-choice task, the rats preferred the sweetened-water more often than cocaine. This effect was further potentiated if the animals were food-restricted and were given the choice between cocaine and a sweet (caloric) solution.
Lastly, and most interestingly, animals that chronically received excessively high doses of cocaine (up to 468 mg, which is the human equivalent of about 750 grams or 214 eight-balls!!!!), still have a moderately low-preference and responding for cocaine over sweet solutions.
Though this research slightly undermines the current hypotheses of drug addiction research, it certainly explains an animal’s biologically-wired inclination to crave sweets, and therefore, definitely contributes to obesity-related research.
Lauriane Cantin, Magalie Lenoir, Eric Augier, Nathalie Vanhille, Sarah Dubreucq, Fuschia Serre, Caroline Vouillac, Serge H. Ahmed (2010). Cocaine Is Low on the Value Ladder of Rats: Possible Evidence for Resilience to Addiction PLoS , 5 (7) : 10.1371/journal.pone.0011592