A single brain stem substrate mediates the motivational effects of both opiates and food in nondeprived rats but not in deprived rats (Bechara 1992a)
Chronic exposure to morphine does not alter the neural tissues subserving its acute rewarding properties: Apparent tolerance is overshadowing (Bechara 1992b)
Deprivation state switches the neurobiological substrates mediating opiate reward in the ventral tegmental area (Nadar 1994)



  • One had black walls and a black Plexiglas floor.
  • The other box had white walls and a wood chip floor.
  • A narrow neutral gray zone separated the two compartments.

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