Time-Dependent Actions of Corticosterone on Infralimbic Cortex Pyramidal Neurons of Adult Male Rats

Area of Science:

• Neuroscience
• Endocrinology
• Stress Physiology

Background:

• Acute stress responses aim to restore homeostasis, involving neurophysiological mechanisms for adaptive coping.
• The infralimbic medial prefrontal cortex (IL-mPFC) regulates behavioral coping styles.
• The role of acute stress and corticosterone on IL-mPFC projection neurons in adulthood is not fully understood.

Purpose of the Study:

• To investigate the rapid and slow effects of acute corticosterone exposure on synaptic transmission and intrinsic excitability.
• To elucidate the roles of mineralocorticoid (MR) and glucocorticoid receptors (GR) in corticosterone's actions on IL-mPFC neurons.

Main Methods:

• Ex vivo whole-cell patch-clamp recordings from layer 5 pyramidal neurons of the IL (L5-IL PNs) in adult male rat mPFC slices.
• Acute application of corticosterone to assess time-dependent physiological changes.

Main Results:

• Corticosterone rapidly shifts the excitatory-inhibitory balance towards excitation via complementary MR and GR actions.
• Corticosterone rapidly and transiently decreases L5-IL PNs firing rate via GR.
• Corticosterone slowly enhances glutamatergic neurotransmission via MR and GR, without affecting inhibitory neurotransmission or intrinsic excitability.

Conclusions:

• Corticosterone dynamically modulates L5-IL PNs physiology in a time-dependent manner, supporting homeostatic responses.
• Rapid effects attenuate IL intrinsic excitability, while slow effects restore IL output function for adaptive executive responses.
• Corticosterone acts as an adaptive signal, controlling IL output to promote context-appropriate responses during stress.