A molecular switch influences addiction behavior and determines how strong the response to addictive drugs is. A research team at Heidelberg University and the Sorbonne University in Paris (France) made the discovery in mice treated with cocaine. The researchers led by Prof. Dr. Hilmar Bading (Heidelberg) and Prof. Dr. Peter Vanhoutte (Paris) demonstrated that the protein Npas4 regulates the structure and function of nerve cells that control addiction behavior in mice. If the quantity of Npas4 was reduced in an experiment, the animals’ response to cocaine was much weaker.