Immediate and Long-Term Effects of Early Adolescent Methamphetamine Exposure on Behavior and Cognition in Mice
Relatively little research has been done to examine the effects of methamphetamine (meth) during early adolescence. Based on data in human meth users and previous data from Dr. Siegel’s lab, it was hypothesized that meth exposure during early adolescence would increase aggression, depression-like behavior, and anxiety-like behaviors, and impair cognition immediately after exposure and later in adolescence.
Mice were administered a binge dose of methamphetamine or saline over a 2-day period during early adolescence. Mice were then randomly divided into 2 groups, with half being tested immediately after injections in early adolescence and the other half during late adolescence. Mice underwent the open field test (test of locomotor ability and anxiety-like behavior), the novel object recognition test (test of object memory), the social interaction test (test of social behavior), the Porsolt forced swim test (test of depression-like behavior), and the resident-intruder test (test of aggressive behavior). Results showed that meth-exposed mice spent less time in the center of the arena in the open field test, which indicates increased anxiety.
In addition, the monoamine oxidase (MAO) inhibitor selegiline, a drug commonly used to treat depression, was utilized in a pilot study to see if any potential effects of meth exposure could be reversed. During adulthood, mice that had no prior injections were administered meth or saline as described above. Mice were then tested in the Porsolt forced swim test. Since mice that received meth showed increased depression-like behavior compared to the control. The following day they received an injection of selegiline or saline 30 minutes prior to the forced swim test. Selegiline was not found to decrease the meth-induced increases in depression-like behavior. This lack of an effect of the antidepressant drug could be due to a variety of factors, including locomotor impairment caused by selegiline, issues with retesting, and the small sample size.
The results of this study demonstrate that meth exposure during early adolescence can increase anxiety-like behavior and meth exposure during adulthood increases depression-like behavior. Further research is warranted to examine the potential reversing effects of anti-anxiety drugs and anti-depressant drugs on these effects.
This work was performed by Sewanee undergraduate student Kayla Pelfrey and Dr. Jessica Siegel. Current work is ongoing in the lab to assess the effects of early adolescent meth exposure on corticosterone levels in serum and the density of dopamine transporters in the striatum. The findings from this study were presented at the Appalachian College Association Summit in October 2013 and the Symposium for Young Neuroscientists And Professors of the SouthEast (SYNAPSE) conference in March 2014.