Stress-induced modification of anxiety in rats is dependent on reproductive status

Pregnancy and lactation are accompanied by behavioral changes that include altered responses to stress. Previous exposure to a stressor can also modulate subsequent stress-related behavior, and this effect is at least partly mediated by the reproductive hormone, estrogen. In this study, we sought to determine if the stress-related behavior of rats that had been exposed to a cat would vary with reproductive status. After exposure to a cat or a nonstress control procedure, pregnant, lactating, virgin female or male rats received two acoustic startle test sessions on consecutive days, followed 4 days later by testing on an elevated plus maze. Startle amplitudes tended to increase across trials in all groups, but were differentially enhanced in nonstressed pregnant and lactating rats. A 5-min exposure to a cat eliminated the enhanced responding in these two groups. The cat exposure attenuated startle stimulus-evoked freezing only in the pregnant rats and produced differential plus maze performance in this group. Cat exposure produced no differential effects in virgin females or males. These results suggest that reproductive state can influence the impact of a stressor on subsequent behavior, but does so in a rather complex way.