Mice and rats on METH

The title of Selective, Retrieval-Independent Disruption of Methamphetamine-Associated Memory by Actin Depolymerization (E.J. Young et al.; 2014) doesn't sound encouraging, and isn't easy to chew through for a laic, but upon doing so you learn that memories made through the use of some drugs are maintained differently than those without. Generally speaking, memories are actively maintained in the brain and even though memories are encoded through structural and functional plasticity, the proteins that maintain them in this state are not all that plastic themselves, leading to their possible modification and fading. However, the memories associated with the use of methamphetamine (METH) tend to be long-lasting and resist extinction, which makes drug addiction an even scarier mental state than it already was (for rats and mice, in this specific study).

In this study, rodents were trained in various Pavlovian setups (with some METH in place of food) and put through food and fear conditioning, and then injected with substances that were hypothesised to affect their METH-made memories and tested for response strength. What was proven after extensive experimentation is that METH-associated memories can be successfully disrupted, though direct actin depolymerization or myosin II inhibition even weeks after the exposure to the drug (under the condition that the rodents made no relapses).

The conducted research brings many more interesting possibilities into light - fear memory and METH-associated memory are both long-term memories, but in the course of the study it was possible to disrupt the METH-associated memory, while at the same time retaining the strength of the fear conditioned memory. This could mean that it might be possible to exclusively target memories associated with specific mental states, while leaving the others of the same type (long-term) untouched, which would have great implications for PTSD sufferers and drug addicts to begin with. Unfortunately, it might be possible that a relapse happens at a later time than that which was considered in the study.

What you should take away from this text is: 1) medical sciences are complicated, 2) you can condition rodents with METH, 3) METH-associated memories are hella strong, but 4) it seems to be possible to singulary weaken them by use of an actin depolymerizing agent (specifically, Latrunculin A).