The dopamine system in the brain mediates feelings of “reward” and is implicated in addiction to various drugs, including anabolic androgenic steroids. Bontempi and Bonci found that the neurological and behavioral effects of androgenic steroids were mediated not by androgen receptors but indirectly by opioid receptors on dopaminergic neurons. A single subcutaneous injection of the steroids nandrolone or testosterone in mice stimulated the release of β-endorphins in a dopaminergic neuron-rich brain region. β-Endorphins activated mu (μ)–opioid receptor (MOR) signaling, which induced excitatory synaptic plasticity in neurons. Blocking MOR activation prevented drug-seeking behavior in steroid-injected mice. The findings may explain the addictive nature of anabolic steroid use.
https://stke.sciencemag.org/content/13/647/eaba1169
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