Calcium ions can enter neurons through either ionotropic transmitter receptors or through voltage-gated calcium channels. Thus, an observed rise in intracellular calcium concentration upon synaptic stimulation can be due to either one of these mechanisms or to both of them. We analyzed the individual contribution of transmitter- and voltage-gated calcium entry in non-spiking somata, acutely dissociated from thoracic ganglia of the locust Locusta migratoria. By optically recording the calcium signal following different stimulation protocols, we isolated the voltage- and the transmitter-gated component and found that these components indeed summate to the total rise in calcium observed under control conditions.