Depolarization of surface-attached hypothalamic mouse neurons studied by acoustic wave (thickness shear mode) detector

Abstract

Isolation of neurons from animal tissue is an important aspect of understanding basic biochemical processes such as the action of hormones and neurotransmitters. In the present work, the focus is on an effort to evaluate the utility of acoustic wave physics for the study of such cells. Immortalised hypothalamic neuronal cells from mouse embryos were cultured on the surface of the gold electrode of a 9.0 MHz thickness-shear mode acoustic wave sensor. These cells, which are clonal, are imposed on the surface of the device at a confluence in the range of 80–100%. The coated sensor is incorporated into a flow-injection configuration such that electrolytes can be introduced in order to examine their effects through measurement by network analysis. Both series resonance frequency, fs, and motional resistance, R_m, were measured in a number of experiments involving the injection of KCl and NaCl into the sensor-neuron system. The various responses to these electrolytes were interpreted in terms of changes in cellular structure associated with the depolarization process. The sensor-neuron system was found to elicit different responses to the addition of KCl and NaCl. Preliminary findings indicate that the TSM sensor does not purely measure changes in the membrane potential upon KCl addition. Typical changes in fs for 15 mM, 30 mM and 60 mM KCl additions were 54 ± 15, 80 ± 26 and 142 ± 58 Hz (mean ± standard deviation) respectively. Typical changes in R_m for these KCl additions were 7 ± 3, 13 ± 4 and 23 ± 6 Ω, respectively. These results were concluded after 17 runs at each concentration. Despite the large relative standard deviations, the dependence of f_s and R_m with respect to concentration was apparent. Controls performed by coating the TSM sensor with laminin or a cell attachment matrix showed no significant changes in either f_s or R_m for the same solutions tested on the sensor-neuron system.