Temporal dynamics of corticosterone elevation in successive negative contrast

Area of Science:

• Behavioral Neuroscience
• Endocrinology
• Animal Behavior

Background:

• Successive negative contrast is a phenomenon where a decrease in reward magnitude leads to a behavioral deficit.
• Hormonal responses, such as corticosterone elevation, are indicators of stress in animal models.

Purpose of the Study:

• To investigate the temporal dynamics of corticosterone response during successive negative contrast in rats.
• To explore the relationship between consummatory behavior shifts and stress hormone levels.
• To examine anticipatory corticosterone elevations in the context of predictable negative outcomes.

Main Methods:

• Rats were trained on a 32% sucrose solution and then shifted to a 4% sucrose solution.
• Plasma corticosterone levels were measured at various time points after the shift (10, 20, and 40 min).
• Anticipatory corticosterone levels were measured before the second postshift session.

Main Results:

• Corticosterone levels were elevated at 10 and 20 min after the second postshift day, but not at 40 min.
• No significant corticosterone elevations were observed after the first postshift day.
• An anticipatory elevation in plasma corticosterone was detected before the second postshift session.

Conclusions:

• The findings support a multistage hypothesis of successive negative contrast, implicating distinct temporal phases of the stress response.
• Anticipatory corticosterone elevations suggest that perceived uncontrollability and unpredictability of aversive events contribute to the stress response.