A new study, published in the journal Nature Neuroscience, studied how the administration of cocaine in mice affected the brain.  Using in vivo imaging, the researchers were able to examine the brain while the mice were alive.  Observing the formation and accumulation of a brain structure called dendritic spines, the researchers concluded that these changes may explain drug seeking behaviors in humans.  These behaviors create major obstacles to overcoming substance use.  According to the National Institute on Drug Abuse, addiction is a brain disease, which may be explained in part by this study.

A press release about the study published on the UC Berkley website reports that the research looked at the frontal lobes of the mice at a cellular level.  Within just two hours of a single dose of cocaine, they had robust and quick growth of dendritic spines.  These are small, twig-like structures that connect neurons, forming the nodes of the wiring in the brain.  Increases in the presence of these dendritic spines as a result of drugs also increased learning about the drug.  As a result of learning about the drug, mice sought out the drug, even to the detriment of other needs.

Researchers used 2-photon laser scanning microscopy, a tool that allows them to make images of nerve cell connections in live mice.  This is the first study to observe these effects in living mice.  Previous research has analyzed mice brains postmortem, finding changes in the density of dendritic spines, but the effects are different for long-term exposure and withdrawal.  This study allows a critical look at the change after the first dose of cocaine.

Mice were put into a box with two chambers.  They had different scents and textures, allowing the researchers to determine which chamber they preferred.  After a preference had been determined, the researchers administered cocaine and placed the mice in the non-preferred chamber.  This altered their future preferences when they were once again allowed to select between chambers.  Mice overwhelmingly picked the chamber in which they received the cocaine.

An article in the Annual Review of Physiology notes that dendritic spines are necessary for synaptic function and brain plasticity.  Abnormal dendritic spines are associated with brain disorders.  In the journal Brain Research, one study identifies changes in spine distribution linked to the neurodegeneration in Alzheimer’s disease and Creutzfeldt-Jakob disease.  Genetic disorders that have mental or neural consequences, such as Fragile X syndrome and Down’s, also show variance in dendritic spine distributions.  Finally, behaviors that impact the brain, including exposure to toxins or alcohol and malnutrition, also alter spine density.