Electrical Control on Neuronal Growth 7

Overview of Electrical Control in Neuronal Growth
  • Discussion on how electrical signals influence neuronal growth and differentiation, specifically focusing on ectodermal cells and growth cones.
Historical Context
  • Ancient Uses of Electricity:
    • Ancient Egyptians utilized the electric Nile catfish for therapeutic purposes.
    • Romans employed torpedo rays for treating ailments like gout and migraines.
  • Benjamin Franklin's Contributions:
    • Famous kite experiment myth: Franklin did not directly conduct it as popularly thought; he used a Leyden jar to store electrical energy.
    • Franklin' invention of an electrical machine led to the popularization of electricity in therapeutic contexts.
  • Dr. James Graham's Temple of Health:
    • Offered electrical therapies, notably the 'celestial bed' for couples.
  • Luigi Galvani and Animal Electricity:
    • Experiments with frog legs led to the discovery of what he termed 'animal electricity' influencing muscle contraction.
Experimental Discoveries
  • Galvani established that electrical discharges affected nerves, leading to twitching in muscles, revealing insights about injury potential.
  • Instruments like the Leyden jar and voltaic pile were critical in subsequent experiments and understanding of electrical phenomena at the time.
Electrophysiology Developments in 20th Century
  • Introduction of technologies to measure small voltages using glass electrodes in organisms like Xenopus embryos.
    • Measurement protocols focused on observing gradients in electric potential across developing tissues (e.g., the neural plate).
  • Non-invasive ion sensing technologies developed for tracking ionic movements and electrical currents in embryos.
Electric Fields and Nervous System Development
  • Electrical Gradients:
    • Presence of trans epithelial potential differences in tissues critical for growth and development.
  • Impact of Hydrogen Ion Flux:
    • Hydrogen ion (H+) efflux correlates with the establishment of neural tissues; necessary for neural induction events.
  • V-ATPase Activity Impact:
    • V-ATPase inhibition leads to decreased neural tube closure and affects critical gene expressions (e.g., Zic3).
    • Involvement in Wnt signaling, relevant for AP axis establishment in embryogenesis.
Role of Electric Fields in Stem Cell Behavior
  • Electric fields direct the migration of human neural stem cells (hNSCs) toward cathodal regions.
    • The behavior of hNSCs influenced by electric fields can be applied to neural positioning and differentiation towards neuronal identities.
Mechanistic Insights Into Growth Cone Responses
  • Growth cones’ behaviors respond to electric fields including directed growth and branching toward cathodal regions.
  • Importance of cytoskeletal dynamics regulated by electric fields.
    • Rho GTPase family involved in regulating microfilament and microtubule dynamics crucial for growth cone guidance.
  • Pharmacological interventions targeting cytoskeleton dynamics can limit or enhance growth cone responses.
Implications for Nervous System Repair
  • Discussion on endocannabinoids affecting growth cone dynamics and their significance in electrical therapies for spinal cord injuries.
    • A balance in using therapeutic electrical fields while minimizing the impact of substances like cannabis on neuronal regrowth.
  • Results from animal studies confirm electric field stimulation can promote axonal growth and enhance recovery of sensory functions in spinal cord injuries.
Future Directions
  • Recommendations for future studies on combining electrical stimulation methodologies with pharmacological agents to optimize neuronal repair post-injury.
  • Understanding natural electric fields can enhance therapeutic strategies for central nervous system injuries.