Comparison of the electrophysiological and immunohistochemical properties of acutely dissociated and 1-day cultured rat trigeminal ganglion neurons

To clarify whether changes to the cellular properties of sensory neurons occur after a brief culture, we compared the electrophysiological and immunohistochemical properties of rat trigeminal ganglion neurons. We compared these neurons after acute dissociation and after a 1-day culture under serum-free and neurotrophin-free conditions. In whole-cell patch-clamp recordings, the 1-day cultured neurons required a lower current threshold to induce an action potential in both small- and medium-sized neurons. Furthermore, the input resistance was higher in the medium-sized neurons after a 1-day culture compared to the acutely dissociated medium-sized neurons. Immunofluorescent studies demonstrated that both the translocation of the activating transcription factor 3 (ATF3) into the nucleus and the expression of a low threshold Na ⁺ channel (Na _v1.3) were upregulated after 1-day of culture. However, in the acutely dissociated neurons, ATF3 translocation occurred at low levels, and Na _v1.3 was not expressed. These electrophysiological and immunohistochemical changes after 1-day of culture were very similar to the reported changes that occur after nerve injury. Our study demonstrated that injury-like characteristics appear to be manifested in the 1-day cultured sensory neurons, which do not occur in acutely dissociated neurons. Overall, our results are relevant and will help when interpreting the results of studies examining dissociated sensory neurons in pain research.