The electrical stimulation of skeletal muscle cells through a tetanic type of protocol (10-90 Hz), generates in addition to the characteristic fast response due to calcium release from ryanodine type of receptors a second long-lasting rise in calcium, most prominent in the nucleus. We have characterized this second calcium signal to be originated by the activity of both the sarcolemmal dihydropyridine receptor (DHPr) and the inositol trisphosphate (IP₃) sensitive receptor activity (1). We have explored the intermediate steps that may link the DHPr and the IP₃ production to obtain this slow calcium signal. The experiments were performed in rat myotubes kept in primary culture for 6 to 9 days. The satellite cells which originate these cultures were obtained from the hind limbs muscles of newborn animals killed humanely following methods approved by the Faculty of Medicine Ethics Committee. The standard electrical stimulation protocol used was a set of 400 pulses, 1 ms duration, delivered at 45 Hz. The field stimulation with this protocol in a whole 60 mm dish of myotubes enabled us to collect biochemical information (1). The calcium signal was monitored in individually stimulated cells preloaded with Fluo-3 (1). In particular, we studied the G protein activation by a pull down assay of the Gβγ subunit, showing a 67± 8.8% (n=3) of G protein activation over the control after the tetanic stimulation protocol. The pretreatment of the cells with a G protein inactivator (pertussis toxin) blocks both the calcium signal and the IP₃ transient. Also, the viral transduction of a Gβγ scavenger (Ad βARK) inhibited the slow calcium response and the IP₃ production as well. These results suggest the participation of the Gβγ subunit of the G protein as a necessary step in the signaling between DHPr and Phospholipase C (PLC) activation in skeletal muscle cells under tetanic stimulation. Overall, these results indicate a novel mechanism of signal transduction by which the DHPr in the sarcolemma acting as a voltage sensor modulates the G protein response that is involved in the PLC activation to provide the nucleus with information about the muscle electrical activity level.