A device for patterned electrical stimulation of cultivated cells: preliminary tests with rat auditory neurons

The number of surviving spiral ganglion neurons (SGNs) is important for the function of cochlear implants. Electrical stimulation has been discussed controversially regarding its protective effects on SGNs both in vivo and in vitro. The aim of this study was to develop a device for electrical stimulation of cultured SGNs. The developed device was first evaluated with cultivated fibroblasts at voltages from 10 to 60 V using biphasic rectangular pulses (pulse width: 10 ms, frequency: 50 Hz, stimulus burst: 1 s, interburst interval: 19 s). Possible toxic effects of 48 h patterned electrical stimulation were evaluated by propidium-iodide flow cytometry of the harvested fibroblasts. Second, the effects of 48-h electrical stimulation at voltages of 6 and 30 V on survival of cultivated SGNs were investigated as a single treatment and in the presence of brain-derived neurotrophic factor (BDNF, 100 ngml) in the culture medium. The results demonstrated constant pH and temperature behavior during electrical stimulation. Furthermore, no toxic effects on fibroblasts up to 40 V were found. The electrical stimulation of cultured neurons did not alter the survival rate compared to unstimulated control conditions. While BDNF application alone showed a significant effect on SGN survival, combination with electrical stimulation resulted in a not significantly increased cell survival. As a limitation of the study, the sensitivity of the described experimental setup appears to be low and only one stimulation pattern has been tested. Thus, experiments using different patterns of electrical stimulation and a more sensitive cultivation setup have to be carried out to fully investigate the effects of electrical stimulation on cultured SGNs. In this context, the developed device can be of help as it provides controlled and reproducible electrical stimulation conditions.