Differences in developing the lever-pressing behavior in two strains of rats

Learning to lever-press for food in rats may be experimentally analyzed according to (a) association of lever-pressing with food reinforcement; (b) development of the behavior of lever-pressing. The latter was studied in two strains of rats with a high or low level of 2,3-diphosphoglycerate (DPG) in erythrocytes. Twelve males from each strain, previously trained to lever-press, were used. The rate of responding increased faster with repeated training-testing sessions in the High Strain than in the Low Strain under the CRF and the FR 10 schedule. The genetic difference in the DPG level in erythrocytes and the resultant long term difference in oxygen transport capability may be a significant factor contributing to the behavioral differences in these two strains.