Intracellular calcium deposition in brain following electrical stimulation

Area of Science:

• Neuroscience
• Biomaterials Science
• Cell Biology

Background:

• Electrical stimulation is used therapeutically for neurological conditions.
• Understanding the cellular effects of electrical stimulation is crucial for optimizing treatment.
• Previous studies have not fully elucidated the ultrastructural changes induced by chronic electrical stimulation.

Purpose of the Study:

• To investigate the cellular and ultrastructural effects of chronic electrical stimulation on the cat cerebral cortex.
• To identify the nature of crystalline inclusions observed in stimulated neurons.
• To explore the relationship between electrical stimulation parameters and tissue degeneration.

Main Methods:

• Bilateral subdural implantation of platinum or rhodium disc electrodes on the parietal cortex of cats.
• Application of electrical stimulation with varying parameters (10 - 300 μC/cm²/ph) for 36 hours over 4 days.
• Evaluation of tissue changes using light and electron microscopy, including electron diffraction and energy-dispersive X-ray analysis.

Main Results:

• Dense crystalline inclusions identified as calcium hydroxyapatite (CHA) crystals were observed in stimulated cortical tissue.
• Intracellular calcification, particularly in mitochondria and postsynaptic dendrites, paralleled degenerative changes like gliosis, mitochondrial swelling, and neuronal loss.
• Phagocytic activity and degenerating cells were prominent in stimulated areas.

Conclusions:

• Chronic electrical stimulation of the cat cerebral cortex can lead to intracellular calcium hydroxyapatite deposition.
• This calcification is associated with significant neuronal and cellular degeneration.
• The findings suggest a potential mechanism involving increased cyclic AMP and enhanced calcium permeability, though the precise electroresponsive mechanism requires further investigation.