Time course of the corticosterone and prolactin response following predictable and unpredictable novelty stress in Rattus norvegicus.
Marked changes in corticosterone and prolactin levels are observed following repeated psychological stress. Furthermore, these responses appear to be affected by the pattern of exposure to the stressor. The present study examined the time course of the corticosterone and prolactin responses following predictable and unpredictable novelty stress. On the fifth day of stress treatment, predictable and unpredictable exposure to the novelty apparatus produced a peak corticosterone response after 15 min of stress treatment. Although corticosterone levels began to decline for both these treatment groups after 15 min, substantially higher levels were observed following unpredictable stress. The steroid levels of animals receiving unpredictable stress treatment continued to be significantly higher than those receiving predictable stress until 30 min post-stress. Predictable stress failed to significantly alter prolactin levels from controls at any of the time points examined. However, unpredictable exposure to the novel apparatus produced high baseline prolactin levels and a subsequent suppression of this response during exposure to the stressor. It was concluded that the differences obtained between animals receiving predictable and unpredictable exposure to novelty reflect a difference in the magnitude of these responses rather than a difference in their temporal pattern.
D000818:Animals; D003900:Desoxycorticosterone / Q000097:blood*; D005260:Female; D007700:Kinetics; D011388:Prolactin / Q000097:blood*; D051381:Rats; D011919:Rats, Inbred Strains; D013315:Stress, Psychological / Q000097:blood*
D003900:Desoxycorticosterone; D011388:Prolactin