Source File:ΔFosB.svg
The finished, wikilink annotated version is currently located at en:Template:Psychostimulant addiction; a more detailed image caption is located there as well.For external (off-wiki) use, a screenshot of the annotated version is located at File:Annotated ΔFosB.svg screenshot.png.
This image shows the signal transduction that occurs in nucleus accumbens D1-type medium spiny neurons that gives rise to psychostimulant addiction.  This signaling cascade occurs during chronic high-dose use of certain dopaminergic stimulants (e.g., phenethylamine, methamphetamine, amphetamine, etc.).

Cocaine induces a slightly different signaling cascade than the one shown here.