Cellular delivery of pulsed IR laser energy has been shown to stimulate action potentials in neurons. The mechanism for this stimulation is not completely understood. Certain hypotheses suggest the rise in temperature from IR exposure could activate temperature- or pressure-sensitive channels, or create pores in the cellular outer membrane. Studies using intensity-based Ca^2+-responsive dyes show changes in Ca²⁺ levels after various IR stimulation parameters; however, determination of the origin of this signal proved difficult. An influx of larger, typically plasma-membrane-impermeant ions has been demonstrated, which suggests that Ca²⁺ may originate from the external solution. However, activation of intracellular signaling pathways, possibly indicating a more complex role of increasing Ca²⁺ concentration, has also been shown. By usingCa²⁺ sensitive dye Fura-2 and a high-speed ratiometric imaging system that rapidly alternates the excitation wavelengths, we have quantified the Ca²⁺ mobilization in terms of influx from the external solution and efflux from intracellular organelles. CHO-K1 cells, which lack voltage-gated Ca²⁺ channels, and NG-108 neuroblastoma cells, which do not produce action potentials in an early undifferentiated state, are used to determine the origin of the Ca²⁺ signals and investigate the role these mechanisms may play in IR neural stimulation.

Date Published: 5 March 2015
PDF: 5 pages
Proc. SPIE 9321, Optical Interactions with Tissue and Cells XXVI, 93210L (5 March 2015); doi: 10.1117/12.2079895

Published in SPIE Proceedings Vol. 9321:
Optical Interactions with Tissue and Cells XXVI
E. Duco Jansen, Editor(s)