Brain extracellular space during spreading depression and ischemia

Area of Science:

• Neuroscience
• Neurophysiology
• Brain Edema Research

Background:

• Extracellular space (ECS) volume dynamics are crucial for brain function.
• Ischemia and cortical spreading depression (CSD) are pathological conditions affecting brain tissue.
• Previous methods for measuring ECS volume changes have limitations.

Purpose of the Study:

• To evaluate changes in extracellular space volume in the rat brain cortex during ischemia and CSD.
• To introduce and validate a novel method for assessing interstitial volume changes.

Main Methods:

• Utilized a new method involving superfusion of the cortical surface with artificial cerebrospinal fluid (CSF) containing extracellular markers (choline or N-TRIS).
• Monitored extracellular concentrations of these markers using ion-selective microelectrodes.
• Induced ischemia and CSD in rat brain cortex models.

Main Results:

• Cortical spreading depression (CSD) induced a reversible increase in marker concentration, signifying interstitial volume shrinkage.
• Ischemia initially showed a slow increase in marker concentration, followed by a rapid rise linked to increased extracellular potassium.
• Both CSD and ischemia resulted in a maximal shrinkage of the extracellular space, reducing it by approximately 50% of the initial volume.

Conclusions:

• The developed method effectively quantifies ECS volume changes during pathological brain states.
• Both ischemia and CSD lead to substantial, reversible reductions in brain extracellular space volume.
• Findings suggest significant alterations in interstitial fluid dynamics during these neurological events.