Comment on

• Loss of morphine-induced analgesia, reward effect and withdrawal symptoms in mice lacking the mu-opioid-receptor gene.

  Matthes HW, Maldonado R, Simonin F, Valverde O, Slowe S, Kitchen I, Befort K, Dierich A, Le Meur M, Dollé P, Tzavara E, Hanoune J, Roques BP, Kieffer BL. Matthes HW, et al. Nature. 1996 Oct 31;383(6603):819-23. doi: 10.1038/383819a0. Nature. 1996. PMID: 8893006