Owing to its unique combination of electrical, physiochemical, and one-dimension structural properties, single-walled carbon nanotube (SWNT) has recently emerged as a novel nanoelectronic biosensor for biomolecular detection with extraordinary sensitivity and simple detection scheme. All the realizations so far, however, are limited to static in vitro measurement. Dynamic detection of biomolecule release from living cells which may occur in millisecond timescale has yet to be demonstrated. In the present work, SWNT network was utilized to directly interface with living neuroglial astrocytes and label-freely detect the triggered release of adenosine triphosphate (ATP) from these cells with high temporal resolution. The secreted ATP molecules diffuse into the narrow interface gap between the SWNT-net and the astrocyte, and interact with the nanotubes. Highly charged ATP molecules electrostatically modulate the SWNT conductance leading to measurable current response. This technique provides a novel platform to study ATP release and signaling which play important roles in astrocyte-neuron crosstalk and other essential cellular functions.