Cognitive deficits linked to methamphetamine and PCP use are driven by a common neurotransmitter switch, neurobiologists demonstrate

The effects of prolonged drug use can manifest themselves in several ways. Memory loss and decreased cognitive function are some of the effects that can persist for years. Neurobiologists at the University of California, San Diego, have now identified a mechanism in the brain that generates drug-induced cognitive impairment.

Scientists from the School of Biological Sciences’ Department of Neurobiology have studied how methamphetamine and phencyclidine (PCP or “angel dust”), which act by activating different targets in the brain, induce similar reductions in cognitive abilities. How can the same memory difficulties arise in response to drugs that trigger different actions in the brain?

The results of this investigation, conducted by Marta Pratelli, scientific assistant of the project, in the laboratory of Professor Nicholas Spitzer, are published in Nature CommunicationsThey showed that methamphetamine and PCP caused neurons to change the way they communicate through a process known as neurotransmitter switching.

Neurotransmitter switching is a form of brain plasticity, a growing field of research that studies how the brain changes its function and structure in response to experience. In recent years, Spitzer and his colleagues have also identified roles for neurotransmitter switching in autism spectrum disorders, post-traumatic stress disorder, and physical exercise.

By examining the cerebral cortex of mice, the researchers found that methamphetamine and PCP each caused a switch from the excitatory neurotransmitter glutamate to the inhibitory neurotransmitter GABA (gamma-aminobutyric acid) in the same neurons in the prelimbic region, an area of ​​the frontal cortex involved in executive functions.

This change was linked to decreased performance on memory tasks since drug-treated mice performed well on tasks when GABA expression was blocked.

Further experiments showed that even after repeated exposure to the drugs, the researchers were able to reverse this neurotransmitter change by using molecular tools to locally decrease the brain’s electrical activity or by using clozapine, an antipsychotic drug. Each of these treatments reversed the memory loss, restoring the mice’s performance on cognitive tasks.

“These results suggest that targeted manipulation of neural activity can be used to mitigate some of the negative effects of repeated drug abuse,” Pratelli said.

In this new study, the researchers found that a drug-induced increase in the release of dopamine, a neurotransmitter involved in reward, and an increase in the electrical activity of neurons in the cerebral cortex were required to produce the neurotransmitter switch.

“This study reveals a common, reversible mechanism that regulates the onset of cognitive deficits upon exposure to different drugs,” Spitzer said.

The researchers note in their paper that a deeper understanding of the brain mechanisms behind drug-related memory loss could boost the prospects for new treatments, leading not only to therapy for methamphetamine and PCP use, but also for other disorders.