Damage criteria for cerebral cortex cells subjected to hyperthermia.

Temperatures above the normal physiological threshold may cause damage to cells and tissue. In this study, the response of a culture of dissociated cerebral cortex cells exposed to laser-induced temperature gradients was examined. The cellular response was evaluated using a fluorescent dye indicating metabolic activity. Furthermore, by using a finite element model of the heating during the pulsed laser application, threshold temperatures could be extracted for the cellular response at different laser pulse lengths. These threshold temperatures were used in an Arrhenius model to extract the kinetic parameters, i.e. the activation energy (Ea), and the frequency factor (Ac), for the system. A damage signal ratio was defined and calculated to 5% for the cells to increase their metabolism as a response to the heat. Furthermore, efficient stimulation with 20-ms long laser pulses did not evoke changes in metabolism. Thus, 20 ms could be a potential pulse length for functional stimulation of neural cells.