“As measured by quantitative in situ hybridization, acute amphetamine induced an increase in substance P , preproenkephalin A and dynorphin messenger RNA levels (+23 +/- 0.05%, +45 +/- 0.07% and +24 +/- 0.05%, respectively).”
“ Chronic amphetamine treatment enhanced only substance P and dynorphin messenger RNA levels (+23 +/- 0.04% and +42 +/- 0.04%, respectively).”