GCaMP8f is a sensitive genetically encoded Ca²⁺ indicator that enables imaging of neuronal activity. Here, we present a protocol to perform Ca²⁺ imaging of the Drosophila neuromuscular junction using GCaMP8f targeted to pre- or postsynaptic compartments. We describe ratiometric Ca²⁺ imaging using GCaMP8f fused to mScarlet and synaptotagmin that reveals Ca²⁺ dynamics at presynaptic terminals. We then detail “quantal” imaging of miniature transmission events using GCaMP8f targeted to postsynaptic compartments by fusion to a PDZ-binding motif.

For complete details on the use and execution of this protocol, please refer to Li et al.,¹ Han et al.,² Perry et al.,³ and Han et al.⁴