The periaxonal space of crayfish giant axons
| Autor: | Peter Shrager, J C Starkus, M V Lo, Camillo Peracchia |
|---|---|
| Rok vydání: | 1983 |
| Předmět: |
Physiology
Sodium Action Potentials chemistry.chemical_element Astacoidea In Vitro Techniques Ion Channels Membrane Potentials Ion medicine Animals Repolarization Axon Ion channel Membrane potential Thin layers Articles Anatomy Axons Electrophysiology medicine.anatomical_structure nervous system chemistry Potassium Ultrastructure Biophysics Neuroglia |
| Zdroj: | The Journal of General Physiology |
| ISSN: | 1540-7748 0022-1295 |
| DOI: | 10.1085/jgp.82.2.221 |
| Popis: | The influence of the glial cell layer on effective external ion concentrations has been studied in crayfish giant axons. Excess K ions accumulate in the periaxonal space during outward K+ current flow, but at a rate far below that expected from the total ionic flux and the measured thickness of the space. At the conclusion of outward current flow, the external K+ concentration returns to normal in an exponential fashion, with a time constant of approximately 2 ms. This process is about 25 times faster than is the case in squid axons. K+ repolarization (tail) currents are generally biphasic at potentials below about -40 mV and pass through a maximum before approaching a final asymptotic level. The initial rapid phase may in part reflect depletion of excess K+. After block of inactivation and reversal of the Na+ concentration gradient, we could demonstrate accumulation and washout of excess Na ions in the periaxonal space. Characteristics of these processes appeared similar to those of K+. Crayfish glial cell ultrastructure has been examined both in thin sections and after freeze fracture. Layers of connective tissue and extracellular fluid alternate with thin layers of glial cytoplasm. A membranous tubular lattice, spanning the innermost glial layers, may provide a pathway allowing rapid diffusion of excess ions from the axon surface. |
| Databáze: | OpenAIRE |
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