4) Vezina P, Kalivas PW and Stewart J: Sensitization occurs to the locomotor effects of morphine and the specific mu opioid receptor agonist, DAGO, administered repeatedly to the ventral tegmental area but not to the nucleus accumbens. Brain Res 417, 51-58 (1987)
5) Nakamura H, Ishii K and Shimizu M: Some altered responses in rats formerly dependent on morphine. Phychopharmacology (Berl) 56, 269-277 (1978)