Sex differences in synaptic plasticity in stress-responsive brain regions following chronic variable stress

Area of Science:

• Neuroscience
• Neurobiology of Stress
• Sex Differences in Brain Function

Background:

• Heightened stress responsiveness is linked to mood and anxiety disorders like depression and PTSD.
• Women exhibit a higher incidence of stress-related affective disorders compared to men.
• Chronic stress induces neuromorphological changes in limbic brain regions.

Purpose of the Study:

• To investigate sex-dependent differences in presynaptic innervation of key brain regions.
• To examine the effects of chronic variable stress (CVS) on synaptophysin density in male and female rats.

Main Methods:

• Male and female rats were subjected to 14 days of chronic variable stress (CVS).
• Presynaptic protein synaptophysin density was assessed in the paraventricular nucleus of the hypothalamus (PVN), prefrontal cortex (PFC), bed nucleus of the stria terminalis (BST), and amygdala.
• Quantification of synaptophysin staining density was performed to evaluate presynaptic innervation.

Main Results:

• Females exhibited higher baseline synaptophysin staining density than males across all evaluated brain areas.
• CVS significantly reduced synaptophysin density in the PVN, BST principal nucleus (BSTpr), and basolateral amygdala (BLA) in females, but not in males.
• Males showed an increase in PVN synaptophysin density following CVS, contrasting with the reduction observed in females.

Conclusions:

• Significant sex differences exist in the organization and modulation of presynaptic innervation in response to chronic stress.
• Chronic stress differentially affects presynaptic inputs to the PVN in males and females.
• These sex-specific neurobiological adaptations may underlie differential stress responsivity and susceptibility to stress-related disorders.