Strain-dependent modulation of memory by stress in mice.

The effects of immobilization stress were investigated in Swiss Webster (Swiss), DBA/2 (DBA), and C57BL/6 (C57) mice, tested in a passive avoidance situation. Retention performance was impaired in Swiss and DBA mice, and improved in C57 mice, immobilized immediately, but not 2 hr, after training. These effects lasted for less than 7 days in DBA and Swiss mice, while they were still present, in the C57 strain, 14 days after training. The naloxone antagonism of the effects observed was also demonstrated. The results are discussed in terms of the possible role of endogenous opioids, stress hormones, and genetic makeup in the stress-induced modulation of memory processes in the mouse.