Methamphetamine blocks exercise effects on Bdnf and Drd2 gene expression in frontal cortex and striatum

Neuropharmacology. 2015 Dec;99:658-64. doi: 10.1016/j.neuropharm.2015.08.045. Epub 2015 Aug 31.

Abstract

Exposure to drugs of abuse can produce many neurobiological changes which may lead to increased valuation of rewards and decreased sensitivity to their costs. Many of these behavioral alterations are associated with activity of D2-expressing medium spiny neurons in the striatum. Additionally, Bdnf in the striatum has been shown to play a role in flexible reward-seeking behavior. Given that voluntary aerobic exercise can affect the expression of these proteins in healthy subjects, and that exercise has shown promise as an anti-addictive therapy, we set out to quantify changes in D2 and Bdnf expression in methamphetamine-exposed rats given access to running wheels. Sixty-four rats were treated for two weeks with an escalating dose of methamphetamine or saline, then either sacrificed, housed in standard cages, or given free access to a running wheel for 6 weeks prior to sacrifice. Rats treated with methamphetamine ran significantly greater distances than saline-treated rats, suggesting an augmentation in the reinforcement value of voluntary wheel running. Transcription of Drd2 and Bdnf was assessed via RT-qPCR. Protein expression levels of D2 and phosphorylation of the TrkB receptor were measured via western blot. Drd2 and Bdnf mRNA levels were impacted independently by exercise and methamphetamine, but exposure to methamphetamine prior to the initiation of exercise blocked the exercise-induced changes seen in rats treated with saline. Expression levels of both proteins were elevated immediately after methamphetamine, but returned to baseline after six weeks, regardless of exercise status.

Keywords: D2 receptors; Frontocortical; Inflammation; Psychostimulant; Striatal; TrkB; Withdrawal.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Blotting, Western
  • Brain-Derived Neurotrophic Factor / metabolism
  • Central Nervous System Stimulants / pharmacology*
  • Corpus Striatum / drug effects*
  • Corpus Striatum / metabolism
  • Frontal Lobe / drug effects*
  • Frontal Lobe / metabolism
  • Gene Expression / drug effects
  • Gene Expression / physiology
  • Male
  • Methamphetamine / pharmacology*
  • Motor Activity / drug effects
  • Motor Activity / physiology
  • Phosphorylation / drug effects
  • RNA, Messenger / metabolism
  • Rats, Long-Evans
  • Receptor, trkB / metabolism
  • Receptors, Dopamine D2 / metabolism
  • Running / physiology*
  • Sedentary Behavior
  • Volition

Substances

  • Brain-Derived Neurotrophic Factor
  • Central Nervous System Stimulants
  • DRD2 protein, rat
  • RNA, Messenger
  • Receptors, Dopamine D2
  • Methamphetamine
  • Receptor, trkB