Modulation of the endogenous opioid system after morphine self-administration and during its extinction: A study in Lewis and Fischer 344 rats

1. Sánchez-Cardoso, P.
2. Higuera-Matas, A.
3. Martín, S.
4. del Olmo, N.
5. Miguéns, M.
6. García-Lecumberri, C.
7. Ambrosio, E.