Corticosterone influences forced swim-induced immobility

Area of Science:

• Neuroscience
• Endocrinology
• Behavioral Pharmacology

Background:

• Corticosterone (CS) is a key stress hormone involved in regulating behavioral responses to stress.
• The forced swim test (FST) is a widely used behavioral paradigm to assess stress-induced behavioral despair in rodents.
• Metyrapone is a pharmacological agent that inhibits CS synthesis by blocking 11 beta-hydroxylase.

Purpose of the Study:

• To investigate the role of corticosterone (CS) synthesis in behavioral responses during the forced swim test (FST).
• To determine if inhibiting CS synthesis with metyrapone affects immobility time in rats.
• To examine the dose-dependent effects of exogenous CS administration on metyrapone-induced changes in immobility.

Main Methods:

• Rats were subjected to a 15-min forced swim test (test) followed by a 5-min retest 24 hours later.
• Metyrapone (CS synthesis inhibitor) or vehicle was administered before the test or retest.
• Corticosterone (CS) or vehicle was administered at varying doses prior to the test or retest.
• Serum CS concentrations were measured before and after the behavioral tests.

Main Results:

• Metyrapone administration significantly reduced immobility time during both the test and retest phases.
• Exogenous CS administration dose-dependently reversed the anti-immobility effects of metyrapone.
• Reduced immobility in metyrapone-treated rats correlated with lower post-stress CS levels and attenuated CS secretion.
• High immobility in vehicle-treated rats was associated with high post-stress CS concentrations.

Conclusions:

• Inhibition of corticosterone (CS) synthesis reduces behavioral despair in the forced swim test.
• Exogenous CS administration can counteract the effects of CS synthesis inhibition on immobility.
• These findings highlight the critical role of CS in modulating behavioral responses to acute stress.