Extracellular calcium and microwave enhancement of membrane conductance in snail neurons.

Microwave irradiation has been shown to decrease the input resistance of snail neurons. In this study, we examined the role of extracellular calcium in triggering the microwave-induced enhancement of membrane conductance. Two sets of experiments were conducted. In the first set, nerve cells were superfused using Ringer solution with added Cd2+ (0.9 mM) which is a known blocker of calcium channels. In the second set, cells were superfused with low Ca2+ (0.7 mM) Ringer solution. Microwave irradiation was conducted at 2,450 MHz for 30 min with a specific absorption rate of 13 mW/g. It was found that 7 mM to 0.7 mM lowering of Ca2+ in bathing solution as well as blocking of calcium channels in neuronal membrane by means of Cd2+ did not influence the fall in membrane resistance induced by microwave radiation. In fact, the observed changed in membrane resistance in these experiments were nearly equal to those observed for neurons superfused by normal Ringer's. Thus, these results rule out the possible contribution of external Ca2+ in the observed microwave effect. Experiments with high Ca2+ solution also support this conclusion.