Oliverio A, Castellano C
Physiol Behav. 1982 Jul;29(1):171-2. doi: 10.1016/0031-9384(82)90384-5.
Exposure of mice to a series of inescapable shocks produced analgesic reaction. This type of naloxone reversible, stress-induced analgesia responds to classical conditioning. Stress-induced analgesia involves activation of the opiate system: thus this type of analgesic mechanism responds to classical conditioning.
