Selective Reward Deficit in Mice Lacking-Endorphin and Enkephalin

  title={Selective Reward Deficit in Mice Lacking-Endorphin and Enkephalin},
  author={Michael D. Hayward and John E. Pintar and Malcolm J Low},
It has been impossible to unequivocally identify which endogenous opioids modulate the incentive value of rewarding stimuli because these peptides are not highly selective for any single opioid receptor subtype. Here, we present evidence based on the measurement of instrumental behavior of -endorphin and enkephalin knock-out mice that both opioid peptides play a positive role. A progressive ratio schedule was used to measure how hard an animal would work for food reinforcers. The loss of either… CONTINUE READING