Simultaneous detection of action potential current waveforms and single ion channel openings in rat cerebellar granule cells.

Spontaneous Action Potential Current waveforms (APCs) and single ion channel openings were recorded in cultured rat cerebellar granule cells using the cell-attached configuration of the patch-clamp technique. APCs were activated without any externally applied stimuli. Both mono- and biphasic APCs were detected with a typical amplitude (positive waveform component) of 25-60 pA. Correlation between cell APCs and inward and outward single ion channel openings immediately before and after the capacitive transients was analyzed. In a detailed analysis it was found that the opening of 1.5 pA inward channel before the waveform was associated with 16%, and the opening of 1.0 pA outward channel after the waveform with 88% of APCs (of total 327 APCs analyzed). The modulation of APC activity by bath application of the amino acid taurine was found to increase the frequency of APCs, transform the APCs from mixed monophasic/biphasic to completely biphasic, and enhance the activated inward current deflections seemingly connected to the increased firing frequency.