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Myelin basic protein depolarizes neuronal membranes
Abstract:
Bath application of 10(-5) M myelin basic protein (MBP) to various types of cultured nerve cells resulted in a membrane depolarization amounting to a change of 41 +/- 15 mV. Excitability could be restored by repolarizing the membrane by means of current injection through the recording electrode. The action of MBP persisted in the presence of tetrodotoxin (TTX), Co2+ or D-600 as well as in low Na+ and low Cl- solutions, whereas it was abolished by increasing extracellular Ca2+ concentrations. The action MBP was mimicked by ouabain. We propose that the effect of the protein might be generated by blockade of an ion pump. It is speculated that MBP may exert a direct effect on neuronal membranes in demyelinating diseases.
Insights
Myelin basic protein (MBP) causes nerve cell membrane depolarization, reducing excitability. This effect, potentially due to ion pump blockade, may impact neuronal membranes in demyelinating diseases.
Area of Science:
- Neuroscience
- Cell Biology
- Biochemistry
Background:
- Myelin basic protein (MBP) is a key component of myelin sheath.
- Demyelinating diseases involve damage to the myelin sheath, affecting neuronal function.
Purpose of the Study:
- To investigate the direct effects of myelin basic protein (MBP) on neuronal membrane excitability.
- To elucidate the ionic mechanisms underlying MBP's action on nerve cells.
Main Methods:
- Cultured nerve cells were exposed to MBP.
- Membrane potential changes were recorded using intracellular electrodes.
- Ionic conditions and pharmacological agents were manipulated to probe MBP's mechanism.
Main Results:
- MBP application induced a significant membrane depolarization (41 +/- 15 mV).
- MBP's effect persisted despite blockade of voltage-gated sodium and calcium channels.
- The action of MBP was dependent on extracellular calcium and mimicked by ouabain, suggesting ion pump inhibition.
Conclusions:
- Myelin basic protein (MBP) directly affects neuronal membrane excitability.
- MBP's action is likely mediated by the blockade of an ion pump.
- MBP may play a role in the pathophysiology of demyelinating diseases by altering neuronal membrane function.