Magnetic field influence on acetylcholine release at the neuromuscular junction

The effects of a static magnetic field on the frequency of miniature end-plate potentials (MEPPs), recorded from the murine phrenic nerve-diaphragm preparation, were studied. In the presence of a 1,200-G field, statistically significant changes in MEPP frequency were observed. There was a modest increase in frequency at temperatures at and below 34 degrees C and a prominent decrease in frequency at temperatures above 35 degrees C. This temperature-dependent phenomenon was not seen in the absence of calcium in the perfusate. These results suggest that, at its phase transition temperature, the diamagnetic anisotropy of the presynaptic membrane is sufficient to influence neurotransmitter release by altering the function of the transmembrane calcium transfer mechanism.