Asymmetrical bipolar nanosecond electric pulse widths modify bipolar cancellation

Abstract

A bipolar (BP) nanosecond electric pulse (nsEP) exposure generates reduced calcium influx compared to a unipolar (UP) nsEP. This attenuated physiological response from a BP nsEP exposure is termed "bipolar cancellation" (BPC). The predominant BP nsEP parameters that induce BPC consist of a positive polarity (→) front pulse followed by the delivery of a negative polarity (→) back pulse of equal voltage and width; thereby the duration is twice a UP nsEP exposure. We tested these BPC parameters, and discovered that a BP nsEP with symmetrical pulse widths is not required to generate BPC. For example, our data revealed the physiological response initiated by a →900 nsEP exposure can be cancelled by a second pulse that is a third of its duration. However, we observed a complete loss of BPC from a →300 nsEP followed by a →900 nsEP exposure. Spatiotemporal analysis revealed these asymmetrical BP nsEP exposures generate distinct local YO-PRO®-1 uptake patterns across the plasma membrane. From these findings, we generated a conceptual model that suggests BPC is a phenomenon balanced by localized charging and discharging events across the membrane.